I updated to 17.24.28 over the weekend and am also experiencing the +5 MPH limitation on an expressway I use daily to work. This makes auto steer useless since traffic typically goes +10 to +15 MPH over the speed limit. Yesterday I updated to 17.24.30 hoping it would fix this, but unfortunately it didn't.
Contrary to the conspiracy theories here, I propose another explanation. Multiple sources have suggested Tesla switched it's data provider from Garmin to TomTom. Perhaps the +5 MPH limitation is not due to a change in the software but rather the data provided by TomTom. For instance, where Garmin may have identified a road as a 4 lane divided road, TomTom may be identifying that same road as undivided. Thus the software is applying the +5 limitation differently.
I'm not saying Tesla didn't change the software, but it's also very possible they didn't and the changes we're seeing are relating to the data provider change. If this is true, the unfortunate thing is it will likely be a permanent change unless TomTom updates it's database. Given how long they've been around that seems unlikely.