Just assume all of it is and treat it as such
These are not my pics but a member on FB. We do mostly only upscale homes and never came across it. But I know its just a matter of time
This is exactly why you dont spray your tile and grout cleaner down, flat mop it on and be a professional.
FLat mopping is ok, I do a lot of wood restoration and mostly removing. Wax off of wood flooring that dosent Belong there, using wax strippers have to dwell and also have to keep reapplying to get all the wax off of the floor. Taping MDF helps but is not fully affective because you have too seal the bottom of the base board to keep the water out and also taping if the paint was just sprayed on will pull off the paint too. What I have done is added a service to Caulk the base to seal the water from impregnating the base board. I explain to the client that these things could happen and offer this service yes it takes longer but for some insurance caulking the base board there helps. Hard to keep from pooling when your scrubbing the floor and also doing the edges by hand then rinse and extract. Weather mopping down your agents or spraying then we have still run across this issue on MDF board, and trust me I have replaced more than I care to admit, but I also have my clients sign a waver in this too. Sitting down with the client and explaining this will also help too so there are no surprises in the end
Most of us install water proof base in bathrooms. And i always use paintable vinyl shoe mould anymore where theres hard surface like LVP. So homeowners can get close to base when cleaning. Im not a fan of just base. Some are. But i think the extra shoe gives the base more detail. And just looks better.