Direct line of fire from that 30mm is of course a whole different matter, but indirect fire from it isn’t that big of a deal (compared to actual tank/artillery) at the receiving end if you have at least some cover. Out in the open that’s of course effective, but I’d imagine a normal house wall would pretty much stop those rounds at 10km.

And even if it wasn’t lethal I’d still keep my head very low if I happened to be on the receiving end, so it’s definitely effective cover fire which allows others to advance.