Can summon entities with the same UUID by pausing the game

Create a new world.

Load only chunks around (0,0)

/tp @s 0 ~ 0
/setworldspawn 0 ~ 0

Summon entity with UUID 0-0-0-0-0

/summon marker 0 0 0 {UUID:[I;0,0,0,0]}

Unload 0-0-0-0-0 entity

/tp 0-0-0-0-0 99999 0 0

Summon another entity with UUID 0-0-0-0-0

/summon marker 0 0 0 {UUID:[I;0,0,0,0]}

✔  Unable to summon entity due to duplicate UUIDs

Pause the game about three times.

Summon another entity with UUID 0-0-0-0-0

/summon marker 0 0 0 {UUID:[I;0,0,0,0]}

❌  Summoned new marker