Hi there. Yes, this is a very low priority issue and impacts very little; however, it does come up.
There’s a lot of documentation about this issue and performance hits on their indexing when using the “Moz Pro” site optimizer. In general, regardless of the permanent 301 redirect, the issue is in regards to first-time behavior speed perception. (2 hops instead of 1)
And yes, this isn’t about really external linking… just fixing the exact 2-hop for the rare HTTP unprefixed alias domain request.
In Nginx/Apache it’s super easy to handle this … not sure how Netlify does it on the backend, but I’m assuming it would be super easy to just detect this case and just avoid the extra 301.
-Mark