sd card internal memory issues

I've never used the "format as internal storage" option (for several reasons), so don't know how this normally looks in a file manager. But just to check the obvious, are you sure when you looked at your SD card you were actually looking at the SD card? I ask because android anyway has a virtual volume "/sdcard", which is actually part of the internal storage, which makes it very easy to get confused here. The fact that the 2 views are identical would suggest that.

However the other odd thing is "25 GB out of 64" vs "12.5 GB out of 17", because 25 is of course twice 12.5 (a suspicious coincidence, though perhaps only that).

If it says you are out of space, what does it show for storage usage now (total via system and separately via file manager)?

When you're microSD card was just a typical 'Portable' card, it was formatted as FAT32 or exFAT. The FAT file system is dated, unsupported but still proprietary (Microsoft), and has all kinds of limitations as storage media with today's technology. But support for it is essentially added to every modern platform (Linux, MacOS, Windows, Android, iOS, etc.) so there's that compatibility factor that keeps it around -- we can take a new card out of its packaging and just use it to transfer files from a computer to a mobile device as is. Convenience over practicality.
But when you manually format a microSD card to be 'Internal', that's a significant change. The card's file system gets changed to ext4, replacing the FAT file system, and it gets encrypted, with the encryption key then tying the card directly to the phone. So that that point, the card is essentially an internal component to the phone -- the phone's internal storage memory and the card's storage memory are now merged as one, now larger file system. The ext4 file system change now matches the same ext4 file system that's the default for Android internal storage media, the encryption key now means you should not physically remove the card now. Aside from creating an Android instability problem, the card's not going to be readable by any computer nor mobile device anyway.

Basically, once you set the card up as Internal, you should stop trying to interact with it in any way. Stop trying to use a file manager app, stop trying to manipulate the card contents in any way. At this point, the installed Android operating system on your phone is managing and maintaining the card as part of the overall storage media.
If you decide later you want to use this card as Portable again, be sure to use the Settings >> Storage menu in this same phone to format the card back to Portable, and be sure to read the warning messages that pop up, This is something of a drastic measure so don't be surprised if later you need to reinstall a few apps.
When the card is Portable again, it's a FAT file system and the encryption removed.