To conform to the needs of the Waze detour detection mechanism, whose purpose is to prevent routing off of freeways and right back on, the segment before the exit and the segment after the onramp (two segments of freeway for example) must have the same name and city name. Supposedly, this means they can also be blank.
At this time, I don't think there is any published guidance but there are some discussions going on. Some editors advocating for removing all city name info from all segments of freeways and ramps. I think this is overkill and isn't representing the map correctly. Also, it makes Waze say "near <city name>" in hazard reports instead of the city name itself.
My guess is that guidance should be that if the freeway segments are fully contained within the city limits, then there is no issue in naming them. But in areas where cities are very tight and there is ambiguity anyway, or the city ends in the middle of an interchange, it may be best to use No city name.
The last item I'll mention, but likely isn't the best idea, is that you can also split the freeway after or before the ramps so that you can name the city correctly around the interchange. For example: https://www.waze.com/editor/?zoom=4&lat=45.34209&lon=-122.76913&env=usa&segments=63702665,63702662. The two segments at the north end of this interchange go to the city boundary. Not sure this is the best idea any longer, but that's in place due to having nothing different to suggest this shouldn't be done in the past. And since things work fine anyway, no real good reason to change it yet either.