File Sharing on MacOS - "connect as" confusion

Hi I've got a question with regards to file sharing on mac. I just upgraded my personal device to a M4 Pro MBP running 15.3 Sequioa. My old device is a 2017 Intel MBP still running 10.15.7 Catalina. Both devices are linked to the same apple id (think, johnappleseed @ gmail . com) I want to access files saved on that via my new device and I enabled file sharing in settings on my old MBP to do so. Now, when I try to connect to the old MBP via Finder > Network > "Old MBP" > Connect As, it prompts me with 3 options for how I want to log in. 1) Guest 2) Registered User 3) Using an Apple Account. I use Option 2 for registered user and type in the correct username and password, but it still connects to the old device via Option 3 (the Apple Account). As such, the apple account doesn't seem to have full disk access and I cannot see files in the Desktop, Documents, or Downloads folders. I can see all others fine (Pictures, Movies, etc.) Even when I click on the device in the Finder bar on the left, it automatically signs me in via the associated Apple account. It's convenient, but useless if I cannot see all my files. Any advice on how I can force it to sign in via Registered User?