Are you using blinded paths and Strike's node is on the blinded path? (I don't know if Phoenix uses blinded paths.)
Otherwise, I'd guess Strike has a bug where it constructs a circular route to ACINQ somehow yet doesn't allow circular payments. I'm not sure how that would happen though. Maybe the node constructing the route is not the node dispatching the payment.
I guessed it’s related to MiCA, but I think you’re right that it’s just a bug. I could select the same options (“self-custody wallet” and “myself”) and withdraw to SN:
Are you using blinded paths and Strike's node is on the blinded path? (I don't know if Phoenix uses blinded paths.)
Otherwise, I'd guess Strike has a bug where it constructs a circular route to ACINQ somehow yet doesn't allow circular payments. I'm not sure how that would happen though. Maybe the node constructing the route is not the node dispatching the payment.