I don't think that you have enough information (data) to know if you have a beef with GM or not.
The range estimate is just an estimate. Does your gas mobile tell you how many miles you can drive on 5/8ths of a tank of gas?
When they did 'whatever', they either unplugged power from everything, OR as part of the update they 'crushed' the old info, and it looks like the computers 'forgot' about range - so the car has to relearn.
If you go on a long drive, and the estimate doesn't change - then I'd be a *little* worried. I would, in fact, plan several trips to take into account "what if" : "what if" the battery goes too low and I am too far from home?, for example. So I would fill up the battery. If it shows (say) 150-mile range, I would plan a trip that got me near home after about (say) 120 miles. After I got back from that drive I'd look at how much battery is remaining, and go for a drive that was 3 miles for each bar (minus one) remaining (i.e., if 4 bars remain, 3x5=15 miles. If 8 bars remain, 7x3=21 miles.) That way you are close to home if/when you get really low on electricity. Personally, I wouldn't want to get much below 10% battery remaining if I were much more than 5 miles from home. That should get you close enough to "not much battery left" for the car to realize how far you can go on 'a tank'.
You do know that there are "5% capacity" bars on the side of the display, that show capacity of the battery (in 5% increments) - right?The above image
shows that the "guess" of range is at 75, with a min (estimate) of 61 and a max (estimate) of 92. The green portion to the left shows that the battery is half full (ten bars, 10x5% = 50%) .The below image
shows that you are getting low on range (bars are now orange) and that about 15% of the battery charge remains (3 bars).