Summoning shulkers which rides small armor stands and has a Peek value greater than or equal to 1 acts normally, but if you die, visually it resets back to 0, but internally it is still the same (proven by overwriting with /data merge).
Also, when trying to step on it in this case, it somehow acts like glitched barriers.

To reproduce:
/summon minecraft:armor_stand ~ ~ ~ {Small:1b,Passengers:[{id:"minecraft:shulker",NoAI:1b,Peek:100b}]}
/kill
/data merge entity @e[type=minecraft:shulker,limit=1,sort=nearest] {Peek:100b}
Stepping on top of that closed shulker will glitch the player in terms of position