Zoglin "IsBaby" entity tag cannot be changed from true to false (1b to 0b) with /data

The bug

Despite MC-65953 being fixed, the IsBaby entity tag for zoglins cannot be changed from true to false (or 1b to 0b) with /data.

Can confirm in 21w07a. Here are some steps to reproduce this issue:

To reproduce:

1. Summon a baby zoglin

    /summon zoglin ~ ~ ~ {IsBaby:1b} 

2. Run the /data command:

    /data merge entity @e[type=zoglin,limit=1,sort=nearest] {IsBaby:0b}

   →  "Modified entity data of Zoglin" is shown in chat but the mob still remains as a zoglin piglet.