Yes, after using recommended option Tvheadend no longer shows data for signal level and SNR. It just says 'Unknown'. And video is as good as it should be.
When that data is updated then video glitches permanently happen, especially on HD channels.

And one more thing to add. My Astrometa tuner ...

Seems to be too often. When I had 1 sec interval check in Tvheadend I had video problems. That setting was by default. I have not tried any other intervals, but used suggested advice to disable check. Disabling it solved the issue and now everything is smooth when using that software.

I got absolutely the same problem with Astrometa tuner. I've tried to use it and ProgDVB to watch DVB-C, but those video glitches are awful. I've contacted Astrometa support regarding this issue. And got reply from their software engineer. Here it is:
"Due to hardware limitation, accessing RF status ...