We dont even know for sure if it is. Like i mentioned a while ago, memory manipulation is a thing in the story for a while now. And there is no one there who could tell if this is the actual OG maya before the time loops.
To disambiguate, I assume your "memory manipulation" means "further altering Maya's memories from
the original time line in addition to the effects of removing all her experiences within the loop".
In principle, what you suggest is possible. There are, however, a few things in this update that make me think the chance of additional memory manipulation happening here is low.
- First is that from Noriko's
Rivals, scenes transitioning between present and wizard age indicate that the dynamics between the two are still similar and recognizable by Noriko. Other lines in the same event such as "Right now, one of them was terrified. And the other was simply...nostalgic" and "Especially now that her brain was a brain again" to me all suggest that her memory as well as her personality are simply reverted back to a state that is complicated but chronologically existed.
- Next is that Noriko actually is a character that can tell if this is the OG Maya or not. However, the incoherence she voices out is: how Maya felt different and how Maya almost lunged at her a second time as if it was Maya's first time seeing her since ages (
When the Sun Sleeps). Both can be easily chalked up to the effect of removing Maya's loop memory without further manipulating her "base memories". And since Noriko hasn't said anything additional, I am going with this
is the OG Maya.
- Last thing is that from the storytelling perspective, tampering with this current Maya's memory
beyond removing her experiences in the loops seems rather redundant and unnecessary. From what we've seen so far, the main purposes of this mechanism is to revise key people's memories associated with the apocalypse while create incoherence from Sensei's POV, and foreshadow the fact that Prime Maya's understanding toward the loop might be incorrect.
Since new Maya no longer holds any cosmic secret, and since there is no reference point to determine whether memories are manipulated or not like you said, I don't see a point in creating fake memories and/or personalities now from a story writing perspective when there is no one to confuse and when Sensei already thinks she is fake enough compared to the Maya he loves. Basically, why write even more fake memories when you already did a substantial personality swapping? This logic may not be stringent, but without any solid sign of memory manipulation followed by a specific purpose, I'd rather believe her memory now, without the influence of the loop, is as close as her OG state gets; otherwise the other option is a rabbit hole that considers everything is possibly fake.
If what you meant is actually "deducting loop memories from Prime Maya doesn't straight equal OG Maya", then sure this is something I would agree on and think about. Other than that, there is a lot less reason to ponder the possibility of new Maya being OG Maya plus some additional memory manipulation simply because this magical macguffin has always been on the table.