I will vouch for the confusion. I too am a new PS 90 owner, and when I read MP-Ohio's post, he is completely inconsistent in referenceing the sear parts.
In the very first pic with the parts denoted as A), B), C), D), he calls part A) an "Auto Sear" and he calls part C) a "Front Sear".
In the numbered descriptions below when he describes the Gen I -IV parts, he completely renames the sears.
He completely disregards the names he established in A), B), C), and D), and talks about a "semi sear" which is not described in the pic he included.
I became very confused by this inconsistency and still am unsure what the "semi sear" is.
Is the "semi sear" part A), the Auto Sear?
Or is the "semi sear" part C), the Front Sear?
I am not a gunsmith, but thinking mechanically, I assume MP-Ohio means the "semi-sear" is part C), the Front Sear.
If my assumption is correct, all reference to "semi sear" needs to be corrected into Front Sear as established as the convention in the pic.
Or conversely, in his part A), B), C), and D) descriptions, he needs to change "Front Sear" into "Semi Sear" so that it is consistent with his Gen I-IV descriptions that follow.