Penal had their DPS increased to be used more often and it lead to chain reaction increasing the DPs of Guards, then shock and now Conscripts.
Well, that's actually wrong.
Guards were not "buffed" overall. They just overnerfed them and then they rectified and the end product remains an inferior unit but "balanced" considering the changes in the overall game. We have already gone through this but for others:
Shocks were not bad because of Penals. Shocks were "average" at best after WFA were released (seeing use only mostly when KV8 was OP) and not worthy after OKW rework.
Finally, the funny thing is that Penals saw no use for years, because they actually made them Riflemen for Soviets. Original design was 6 man G43 squad with the same premium cost as PG.
Conscripts: as i said before, i just hope that the cover bonus is just slight over the top for people to actually try it. This is just a common practice when you implement a new feature.