Before automatically signing into my microsoft account, my gamertag/username displays skinstandardcust. 

How to reproduce

Load minecraft bedrock.

And wait for the game to load, you might get the same username before signing in.

Observations 

Username/gamertag is skinstandardcust.

Expecations

It always has to be my original username. 

Another reason for this could also be because it take about 10 seconds to sign into my microsoft account so this odd username shows up, which is why I think its best if the game signs you in before launching the game if possible.