The Teslas should be fine, but submersion is really not recommended and this is getting really close. The breather valves can leak if subjected to enough force.
Leaking leads to corrosion which leads to really expensive repairs.
In a traditional ICE car or an ICE/EV/PHEV platform I can imagine there are more options to put things higher up within in the front chassis.
Interestingly I wonder if it's an issue of just a difference between the two designs in terms of scenarios its optimized for (a.k.a. there's a tradeoff).
If the EV's skateboard battery water seal is functioning perfectly then EV will perform well, perhaps better than a traditional design ICE/EV/PHEV platform.
If the EV's skateboard battery water seal has been compromised, then due to its relatively low placement, a lower than normal water levels may cause significant damages.
Water Damaged Tesla Model S Battery