defaultTokenChangedHandler sending expired id tokens to login api endpoint

[anishadoni]

I confirmed through logging that the defaultTokenChangedHandler occasionally sends an expired id token to my login endpoint.

This line in particular is stumping me

const userToken = await authUser.getIdToken()

My understanding is that this should automatically refresh an expired id token. However I can clearly see in my logging in the backend that expired tokens are being sent. How is that possible?