Highly questionable conclusion, especially without seeing it in person.
A more concise way to look at this:
If the original color is no longer present, all subsequent seal coats had to be abraded away before you even hit that color layer. If that color layer is gone as well, it's raw enough to be considered unsealed wood.
Yep, some of the deeper, open pores can still block a little finish, as they likely were filled in the finishing process, but hardly what I'd call "sealed", as we're talking pinprick size pores being plugged, not a light, even coat left on the surface that will block your sweat, which is what I'd define as actually sealed, and seems to be at the root of your question.
Just trying to clarify why you're being told it's sealed, yet advised you need to seal it....
Final point I'll strongly agree with: De-waxed shellac. Look for Zinnser Bulls Eye Seal Coat, avoid their straight shellacs. It can be stripped off later with alcohol, which is the solvent it's carried in and can be re-dissolved with. That, and a judicious amount of sanding should allow you to work with a fresh stain reasonably well once the time comes.