I tried it on creatures I thought were lizards: "Kobolds, Troglodytes, Lizardmen, etc."

They werent high level either, and Im able to turn high level undeads, I was wondering if this ability was functionning adequately?

or if lizard was restricted to: Deep lizards only.

Not a bug.

It's not supposed to work on all reptilian creatures -- in particular, it shouldn't be working on "intelligent" reptilian creatures like kobolds, yuan-ti, lizardfolk, and troglodytes. It should be working on deep lizards, stone lizards, and any other creatures that claim to be proper lizards.