When summoning a falling block with command no.1 everything seems to work as intended, and a falling red wool block appears (time set to -9999999 in order to keep it from dying).

/summon minecraft:falling_block ~ ~ ~ {NoGravity:1b,Time:-9999999,BlockState:{Name:"minecraft:red_wool"}}

However when using the data command in order to change the Block State, the block model doesn't change even though the Block State is now changed.

/data merge entity @e[sort=nearest,limit=1,type=falling_block] {BlockState:{Name:"minecraft:blue_wool"}}

Fixes itself when relogging