Looks like it allows people to turn right, but not go straight or make U-Turns. It looks like cars are allowed to go straight, but maybe there's no reason to route like that and it prevents offramp to onramp routing.
This is exactly the reason the cross streets are there, which i edited and categorized as ramps before it was switched to service roads. There are plastic barriers in place at that cross junction positioned in a way to force drivers to make a turn right to the connecting highway and not go straight or u-turn.
The point raised about service roads affecting long-distance routing is a good one, and it didn't occur to me before.
As for the local guidelines, there is a FAQ in a FB group (which I need to get around to porting over to the Waze wiki so that it's accessible to anyone without a FB account), there is this statement for ramps:
When traffic moves between two roads or highways that are at different grades without the use of traffic lights or stop signs, they use ramps. The typical example is the on-ramps or off-ramps of a highway. Roads connecting a highway with a rest/service/parking area should be treated as ramps as well and named accordingly (e.g. "Exit to Service Area").
When traffic moves between two roads that are at the same grade, these connecting segments are not technically ramps to Waze. These cases should be treated as At-Grade Connectors. Access roads to highways at the same grade are service roads (see below)
Only exception from the above rule of Same-Grade-Connector should be a ramp if it's a signed, numbered exit of a highway (like Exit 116 Rawang on E1 North-South Expressway (NSE Northern Route).
The bolded sentence is probably the guideline being used here. It implies that roads that connect highways at the same grade should be service roads, which I don't agree with.
The section about service roads is not too different from the standard wiki.
7) Service Roads
These are streets that are typically adjacent to a freeway (or major highway). Also called Frontage roads in some states. These could be access roads to the highway itself, but have the property of a regular or primary street.
Service Roads is also used for 1 lane wide kampung (village) road with tarmac but poorly maintained with lots of potholes n bumps but still accessible by all vehicles. Roads paved with crasher runs must use Dirt Road / 4x4 Trail