No, no issue at all. Not dualbooting either.
I ran a DOS-based diagnosis tool from Samsung called ESTool
and it offered low-level format and other options to reset the drive's reported size to its native size. Oddly, the native size is 625142448 but it would only "reset" to 625142447, exactly one sector less. However
, I unexpectedly solved the issue by simply wiping the HD with a diskpart -> clean
command and then restoring my latest system backup to a freshly created partition. Now the drive reports the old, proper CHS data again.
Totally weird, as I was convinced it was a problem with the drive's own firmware settings. But...chalking this one up to the God of Computing Glitches and marking it solved.