Looked back through some old Whistler posts. To put into perspective what transpired in the GRE to Whistler transition I found the below posts interesting...
WS-1080 same rebranded PSR-800
WS-1095 same rebranded PSR-900 There were PSR-900 beta units in the field Don Starr had one tersting there was one at the Las Vegas show
RS PRO-668 Rebranded PSR-800
What has Whistler designed and it took over a year to rebuild scanners already built and designed so what have they designed and built?
GRE let the product lapse and as a result, several of the key components went into EOL. Drop in replacements were not readily available causing several circuits to be re-engineered before it could be built.
Not a single tool was recoverable from the GRE purchase and as a result Whistler had to tool all the housings and brackets from the original drawings.
The PSR-900 you refer to may have looked the part but it was far from complete both in hardware and software not to mention the issues stated above.
To state that Whistler took a year to rebuild scanners that were already being built is not a fair representation of what actually occurred.
GRE: repackage a PSR-800 and call it a PSR-900
Whistler: make the thing work and call it a WS1095
More time was spent by Whistler getting the WS1095 to actually work than was spent by GRE creating the PSR-900 in the first place.