The T actually means that a talkgroup has been confirmed to be TDMA mode, not just capable of it.
A couple of problems with this statement:
1. If you hover over the Mode heading on the column, the tooltip says otherwise: "T = TDMA Capable Talkgroup"
2. In some systems, talkgroups are dynamic and can be in TDMA (Phase 2) at one moment and FDMA (Phase 1) at other times - which is known as
dynamic dual mode (DDM) -- it all depends on what subscriber radios are actively on that talkgroup (i.e. if a non-TDMA radio switches to and is allowed to affiliate with the with that system/talkgroup, the talkgroup ill revert to FDMA/Phase 1 as long as they are on the talkgroup - even just listening).
On a related note -- "E" (for encrypted) exposes similar characteristics -- some talkgroups are full time encrypted and others are part time/some times encrypted. The "E" can be misleading making you think the talkgroup is always encrypted.
Of course, all of this is subject to whatever the submitter of the information provided. For example, TDMA (Phase 2) is listed as "T" if the submitter provides that info (or if the system is known to be 100% TDMA) but I suspect the default is "D" since TDMA is still digital.
And, although many systems are listed as "TDMA" or "Phase 2", they can be operating entirely in Phase 1 mode. I know of several systems that are listed here as "Phase 2" but in fact are operating as "Phase 1". Some of this comes from vendor announcements or propaganda stating they are deploying a "Phase 2 compliant" system which means that at some point (could be day 1 - could be never), all of the subscriber radios on the system will become "Phase 2" and then the system will really be "Phase 2"... or, because of easing of the rules, may never become Phase 2......
Since some talkgroups can be TDMA, and automatically revert back to FDMA when a Phase I-only radio is present, the Auto mode is best if the scanner has it.
Also - Phase 1 or Phase 2 - if doesn't matter - they are both digital. "Auto" is this case really doesn't (shouldn't) matter. If the "system" is pure digital (vs. and legacy mixed-mode P16 system), the system itself will (or should) cause the talkgroups to be processed as digital anyway.