The method net.minecraft.entity.EntityLiving.onInitialSpawn(DifficultyInstance, IEntityLivingData) (or rather the methods overriding it) does not check if the additional mob for spider or chicken jockeys collides when they are spawned.
This report is not about ridden entities not considering the passenger height when moving, suffocating the passengers. That is reported as
This can currently be seen with
MC-103516 where the skeleton stands with its head in the glass block.
Based on 1.11.2 decompiled using MCP 9.35 rc1