The OPSPEC (A050) and GOM make no mention of another STC.
FYI: As I no longer have access to these docs did some more checking. The NVG IMC statements I remember were either listed in A050 or the GOM depending on operator. However, it appears the original A050 templates have been revised due to conflict issues with other OpSpec sections (e.g. A021) and the IMC statements were dropped in favor of straight VFR visual minimums whether aided or unaided with the IFR requirements separate. Was told the concern with NVG and IMC was that some goggle systems were capable of seeing through light fog and rain that could lead to entry into total IMC. That is the reason behind the current guidance above to drop the goggles if enter IIMC and follow those procedures. Couldn't find an original A050 template but did find an older A051 template (airplane NVG) that had the no IFR limitation I remember shown below.
(c) The certificate holder is authorized to use NVGs only to aid night flight during VMC
and must not use NVGs during instrument meteorological conditions (IMC). The certificate
holder must comply with VFR weather minimums during ANVG-aided flight and must adhere to
the weather minimums prescribed in these operations specifications and all applicable FAA
regulations.
https://www.faa.gov/documentLibrary/...N_8900.388.pdf