Yes, the blockers in Mild 22 seem to be relic from the first releases of LPDOS, which still used times bombers.
Mild 24: With a Little Creativity...Lemmings: 50
Save: 50% = 25 lemmings
Release Rate: 50
Time: 5 minutes
Skills: 20 of everything
Good: There are quite a few different solutions, but none that is obvious for non-experts. The skill set and the terrain layout forgive the player several mistakes like digging too deep or bashing too far beyond the exit.
Okay: The older versions, that were not yet based on the NeoLemmix engine, are good for studying glitches/odd behaviours in Lemmings, e.g. try saving 48 lemmings with only 1 blocker, 1 bomber and 2 bashers.
Bad: Rather bland level without much decoration.