The key word there being "seen", I reckon. And we all know how good the media/politicians are these days at coming up with narratives for elections that actually line up with reality.............
Take Montana and Georgia in particular - if the "story" of these elections was "referendum on Trump", then Republicans failed pretty bad in Montana, whilst holding their own in Georgia. But if you treat it as a more standard election (ie. comparing to 2016/2014 house results), then the interpretation is pretty much the other way round! Try getting a definite picture out of that.
Having said that I think Republicans would do well not to just ignore the average swing there (which lines up sorta well with
generic ballot polling). But when it's difficult to measure how competitive these races actually are to begin with, plus the quirkiness you can get with special elections (uncertain turnouts, spending, coverage etc), it's probably a bit silly to try and paint these results as a clear morale boost/loss for either side.