When a player places a spawner that has NBT data associated with it, none of the NBT data is applied to the placed spawner.

For instance, if I run the command /give @p spawner{SpawnData:{id:"minecraft:skeleton"}} and then try to place the resulting spawner, it turns into a pig spawner instead of a skeleton spawner. The same happens with SpawnPotentials and other spawner specific NBT tags.