Driveway ramps are what I call the blocks of either rubber or cement that go in the gutter to make it easier to drive up over the kerb into a driveway e.g. Driveway Approach – JLC Ramps – for better compliance with council requirements (*)
What do / would we call them in OSM?
I’d tag it kerb=lowered.
"Lowered kerbs are often found at crossing and driveways. They help ensure the crossing can be used by wheelchair users and allow access to drives.
Some names for objects that fall into this category include driveway apron, curb cut (U.S.), curb ramp, dropped kerb (UK), pram ramp, and kerb ramp (Australia)." from https://wiki.openstreetmap.org/wiki/Key:kerb
kerb=lowered implies wheelchair=yes
Some of the pictures in the first link show a big gap which might be too wide for some wheelchairs.
You misunderstood the question. These ramps are not a kerbstone. They form an attachment to the kerbing, which can be kerb=raised eg https://www.barriersdirect.co.uk/traffic-management-c1220/wheel-stops-trench-ramps-and-cable-hose-protection-c1152/kerb-ramp-heavy-duty-suits-most-kerbs-quickly-deployed-customer-recommended-p4442 for a wheel-only width.
ramp= or eg ramp:motor_vehicle= could be added. This leaves kerb= for the original kerbing. There are other such ramps at kerbs for wheelchairs, trolleys, and carts. (Of course, they should be persistently installed, not temporary) Use wheelchair=no as needed.