If the gamerule maxEntityCramming is set to 1, riding a mob inflicts damage

Related to MC-270569, MC-270532, and MC-270568. Since entities being ridden cannot be targeted, and riders aren't pushed by what they're riding, it's illogical for maxEntityCramming to consider the rider and their mount as colliding. However, when the gamerule maxEntityCramming is set to 1, players or mobs riding a mob suffer damage, as if the passenger and vehicle were colliding.

Steps to reproduce

1. /gamerule maxEntityCramming 1

2. /summon minecraft:pig ~ ~ ~ {Saddle:1b}

3. Ride the pig in survival or adventure mode

Observed Outcome: Suffering damage leading to death. Interestingly, the pig remains unharmed.
Expected Outcome: No damage should occur.