using /data command to attach boat to happy ghast gets wrong leash display

Using a command to attach a boat to a happy ghast connects a leash, but not the four-point leash. Using the tags I’ve assigned, I use the following command:

/data modify entity @n[tag=ghast_boat] leash.UUID set from entity @n[tag=colorings_ghast] UUID

When I do the connection manually, I get the right leash.