No it prevents those compounds from reducing to more androgenic forms. They are still effective regardless.
Again propecia will do NOTHING for compounds that dont use the 5 alpha reductase enzyme. It can not, nor will not block any androgenic effects from other androgenic compounds period. There is absolutely no way this can happen. It can protect against testosterone, and boldenone from becoming more androgenic compounds (dht,dhb). That is all it can help with.
There are topical things that can help with other compounds (spirolactone, nizoral shampoo, azelic acid etc)