MCPE-60667 is probably best and most highly-upvoted duplicate issue to link to.
I confirmed that the Xbox One can see and join LAN games when the account has an Xbox Live Gold subscription. I don't like that this is the case, but it confirms the situation.
@ashley my experience has been that the xbox has always been able to see the lan as long as the account has xbox live, and as long as the account has permission to play online games, as described in this issue :shrug:
I will comment that this is a relatively expensive bug for customers who want to play as families on LAN and who have to pay for Gold every month to do so. Hopefully this issue gets more attention soon.