Legality of HobbyFix AR variants in the US

As some of you may know, the US BATFE has adopted stricter guidelines of late concerning partially finished receiver blanks (a.k.a. 80 % lowers) for AR-series rifles. Essentially, once a lower receiver has *any* metal removed from the fire control group area, the lower is considered a firearm by the BATFE.

From what I understand, the HobbyFix AR models have the same receiver dimensions as the "real steel." I suspect this makes these models illegal to import into the US (cf. the Inokatsu airsoft m4s that are prohibited for the same reason).

Could anyone confirm this to be the case?

What I can confirm is that the receiver dimensions are very slightly off, so a real upper may fit on a HobbyFix lower, but may need reworking at the pivot pin and takedown pin for a snug fit.

A HobbyFix upper won't fit on a real lower without reworking at all.

The problem may be recognizing that it is a toy modelgun lower receiver. The uppers are designed differently in the barrel extension area, but the lowers just look real, especially the late M4A1 and M16A4 lowers. The early M16A1 and XM177E2 receivers had a distinctive extra "HF SMG" marking the later lack.