The Supercharger 25 miles away from us -- and no, I don't use it for daily charging! -- also has a general parking allowed sign. So even if an ICE driver normally wouldn't park there, the sign is like an invitation and once parked it seems unlikely the time limitation will matter. Oddly, there is tons of ICE parking closer to the restaurant nearby.
This is what I typically see at Supercharger stations, especially the ones in hotel parking lots, the most common kind IME. The usual setup is to have half the Supercharger spaces marked for EV charging only and half for time-limited general parking: 30 minutes, 60 minutes, or 2 hours. This likely because the landlord is required to have a certain number of customer parking spaces by the municipality and Tesla negotiates to have half marked EV only and the rest posted for time-limited general parking. Not that the landlord is going to tow customer's cars even if they are parked in the wrong spots.
The only two Supercharger Stations, for which I have pictures, that are all marked EV only are Grand Junction CO (shopping mall) and Salt Lake City (Tesla owns the property). Others that have general parking allowed:
(pardon the low resolution, these were cropped from distant photos)
^ Glenwood Springs CO, hotel, 2 hours general parking (several of the stalls are blocked by traffic cones to keep them available)
^ Silverthorne CO, Starbucks parking lot, 30 minutes general parking
^ San Diego (Mira Mesa) CA, Qualcomm parking lot, 30 minutes general parking
^ Price UT, hotel parking lot, 30 minutes general parking
^ Green River UT, museum parking lot, 60 minutes general parking
^ Centralia WA, shopping center parking lot, 30 minutes general parking in seven of ten stalls
^ Moab UT, hotel, 2 hours general parking (ICEing is common overnight due to limited space in the hotel lot)
That's just the ones for which I have pictures; a split between EV parking and general parking is the most common setup I've come across on my road trips.