You backup exactly what I have observed first hand as well.
In nearby saginaw, midland counties that have 4 tower systems, people I worked with on rs pro 651-652's, ws1040-1065's and other whistler models asked why after a couple days no reception of any kind on those systems. Pro106-197s when they were sold, saginaw was the only simulcast and never had anyone say no reception at all like whistlers, other than the occasional garbled audio.
When the 651-652s came out, I originally thought maybe it was their radio or my programming, but then I added one scanlist with the attenuator on, threw different decoding numbers in the expert settings, people still would report no reception. I tell em try to lower the antenna on the desktops, move their radios around, even tell em the paperclip antenna method.
Occasionally the whistler made ones apparently work, but I explain to people about your location and where the towers are. I recall one fellow that said his 1065 worked well in Saginaw, but also lives maybe 1 mile away from a tower.
Whistlers don't do well in simulcasts. Here is review of the high end TRX1 in four tower Saginaw county. Need to view the entire video.
If I get asked what scanner to get and they are in a simulcast county, I strongly suggest Uniden, those models do work better in simulcasts especially with the latest firmwares. Granted everyones 'mileage will vary'.