if that units are still recruiting, u still receive the original resource back.

So if u recruit 1 armor infantry, 12% overhead. U'll need 112 metal, but if u cancel the training, u will only get 100 metal back.

Recruited units, however, won't give u back resources.

That's nice, because it's always possible to click the wrong unit configuration, but one has at least two ticks to change it without losing it.

But still, disbanding a recruited unit should give some "scrape" IMHO. After battles there are salvaged resources, which is far less realistic to get anything if a fleet was destroyed. I mean distroyed (dismantled in uncontrollable manner) vs disbanded (dismantled in base, under controlled conditions).