If you summon let's say a chicken riding a pig, with the chicken having the nbt data

{CustomName:Bob,CustomNameVisible:1}

, It doesn't show the name.

Recreate:

Type in a command block:
/summon Chicken ~ ~1 ~ {Passengers:[

{id:"Zombie",CustomName:"bob",CustomNameVisible:1,IsVillager:0,IsBaby:1}

]}

CustomNameVisible:1 doesn't work.