I thought ham radios at least were required to meet the requirements laid out in the portion of the FCC rules regarding ham radio, which is called Part 97. Every ham radio design that is to manufactured must be type accepted for ham radio use which means conducting sophisticated RF measurements to be sure that it operates correctly according to Part 97 rules, and then submitting the results from those measurements to the FCC. Only once a specific ham radio equipment design (circuit design, RF shielding, etc) has been type accepted by the FCC based on Part 97 rules can it be legally sold in the US as a ham radio. If any of the design is to be changed (like if the manufacture decides to make a new circuit design that's more efficient), it must undergo the whole type acceptance process all over again (RF testing and submitting the test results to the FCC, and then receiving a letter of type acceptance from the FCC), before devices built with the new design can be legally sold in the US as ham radios.
Part 15 on the other hand, is for either unintentional radiators, or for low power intentional radiators that operate in bands that don't require a license for low power use, and that aren't already covered by other FCC rules (such as the CB radios that are covered by Part 95).
If HAM radio transmitters required type acceptance, HAM radio operators could not build and then use their own transmitters and amplifiers. It is the HAM radio operators responsibility to operate within the technical specifications and operational rules in Part 97.
As I recall, Part 97.315 was added to address the problem of HF amplifiers and especially 10 meter amplifiers sold and used on 11 meters. It does no prevent a HAM radio operator from building or modifying an amplifier for use on 10 meters or other HAM frequencies below 144 MHz.
§97.315 Certification of external RF power amplifiers.
(a) Any external RF power amplifier (see §2.815 of the FCC Rules) manufactured or imported for use at an amateur radio station must be certificated for use in the amateur service in accordance with subpart J of part 2 of the FCC Rules. No amplifier capable of operation below 144 MHz may be constructed or modified by a non‐amateur service licensee without a grant of certification from the FCC.
(b) The requirement of paragraph (a) does not apply if one or more of the following conditions are met:
(1) The amplifier is constructed or modified by an amateur radio operator for use at an amateur station.
(2) The amplifier was manufactured before April 28, 1978, and has been issued a marketing waiver by the FCC, or the amplifier was purchased before April 28, 1978, by an amateur radio operator for use at that operator's station.
(3) The amplifier is sold to an amateur radio operator or to a dealer, the amplifier is purchased in used condition by a dealer, or the amplifier is sold to an amateur radio operator for use at that operator's station. (c) Any external RF power amplifier appearing in the Commission's database as certificated for use in the amateur service may be marketed for use in the amateur service.
47 CFR subpart J part 2 is quite lengthy, but 47 CFR Part 97.315 is rather short.
The link below takes you to subpart J part 2 as referenced above in 47 CFR Part 97.315
subpart I part 2.815 referenced above.
§ 2.815 External radio frequency power amplifiers.
(a) As used in this part, an external radio frequency power amplifier is any device which,
(1) when used in conjunction with a radio transmitter as a signal source is capable of amplification of that signal, and
(2) is not an integral part of a radio transmitter as manufactured.
(b) No person shall manufacture, sell or lease, offer for sale or lease (including advertising for sale or lease) or import, ship or distribute for the purpose of selling or leasing or offering for sale or lease, any external radio frequency power amplifier capable of operation on any frequency or frequencies below 144 MHz unless the amplifier has received a grant of certification in accordance with
subpart J of this part and other relevant parts of this chapter. These amplifiers shall comply with the following:
(1) The external radio frequency power amplifier shall not be capable of amplification in the frequency band 26-28 MHz.
(2) The amplifier shall not be capable of easy modification to permit its use as an amplifier in the frequency band 26-28 MHz.
(3) No more than 10 external radio frequency power amplifiers may be constructed for evaluation purposes in preparation for the submission of an application for a grant of certification.
(4) If the external radio frequency power amplifier is intended for operation in the Amateur Radio Service under
part 97 of this chapter, the requirements of
§§ 97.315 and
97.317 of this chapter shall be met.