I have a teleport command for squids that don't change their y-value, but they don't fall at all and seem to desync from one of my other commands to summon a falling block at their location.
Commands used:
/execute as @e[type=minecraft:squid] at @s run summon minecraft:falling_block ~ ~ ~ {BlockState:{Name:"minecraft:birch_planks"},Time:0,NoGravity:1b}
/execute as @e[type=squid] at @s run tp @s ~0.03125 ~ 0
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[media][media]
Can confirm in 20w51a.

In 21w11a

In 21w13a

In 21w14a

In 21w15a

In 21w17a

In 21w18a

In 1.17

This actually affects all mobs, not just squids. See MC-104494. The desync part seems to have been fixed in some 1.14 snapshot.