Single-row IMS/IMS bearing in 2.5L M96?

[986FTW]

Hello all! First post here!

I have a 1998 Boxster that apparently has a Porsche factory replacement engine installed (it has an "AT" code after the "M96/20" in the engine S/N). The engine has an "X" year model code, so the block should be from 1999.

Porsche has no record of the engine replacement, and I'm trying to determine if it is a drop-out from another warranty-replacement car.

Here's the really odd thing: The IMS is the later type that only accommodates the single-row IMS bearing.

Would Porsche have manufactured this "AT" coded 2.5L M96 with a single-row bearing? Or must someone have rebuilt it with a new, single bearing IMS and IMS bearing?

Many thanks for any guidance that you may offer!