From the looks of the Bimba website the described cylinder would not be FRC legal.
Quote:
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MRS cylinders have an additional groove in the piston to accommodate a magnet. They differ from the Moption because they combine features of the "Z" line with Original Line construction. Type 303 stainless steel rods are standard.
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Emphasis mine
This makes it sound like they differ in more than an "optional attachment part"
However, as Leav noted, the Q&A is the only source for a definitive answer.