Granted, you’re using a home setup. But you could still consider setting up the VPN on a central AP and repeating your hotspot through it to make everything going in and out of your network encrypted and more secure. None of your actual traffic (besides what your phone is emitting) will be in the clear, which is better than nothing.
Almost any router with VPN and repeater options will accomplish this if you don’t wanna root your phone. I’ve flashed OpenWRT on the equivalent of router potatoes over the years. It’s pretty straightforward.
I’ve used wi-fi calling fairly extensively mostly because I’ve lived in areas where there was zero cell service but ready access to internet (via Starlink or other wireless forms of it). One thing I do know is that my phone co. requests that I fill out a form specifying where I am living currently (whilst using it) so that if I ever need to contact emergency services they’ll have a better idea of where to route the call to. For instance my phone number originates from Western BC but I could potentially be using wi-fi calling from anywhere in the province. I mention this to say, it appears my telco doesn’t have a way to triangulate me with this service.
I can further attest that wi-fi call & text reception still works fine when I have a VPN running on the router that my mobile device is connecting to. Make of that information what you wish.
Though that I have read that wi-fi calling is atrocious for privacy reasons that I have not followed up on. Given the above I’m not sure how or why that would be the case, but basically if I’m in an area with cell coverage I turn it off. I’ve always meant to look deeper into how or why it might be bad (or worse) in some way.