Sankis

I'm back to KSP after a long while away and am playing a heavily modded game in 1.12.3 now. ReStock is one of the mods I'm using and it's wonderful! Thank you for all your work on it. One question, though: I've noticed that when I go into "advanced" mode and sort by engines I can find an SRB called STS-01 "Anvil". It does not appear to be in any category, though so I can't plac eit outside of advanced mode. Is this intended behavior for the part (deprecated maybe?) or have my many, many mods messed something up?