Dude. People do rewrites on the day. There may not be "major script revisions", but there could be fairly significant tweaks etc. - virtually every show does minor rewrites on a near-daily basis and those will all be lost. The dialogue will be clunkier, the scenes will work less well. It's just a question of how much those 19 days will matter - like how much they were actually going to get done?
And they have lost the showrunners, which is pretty major. Any show that's consistent is going to feature regularly daily input from the showrunner(s). Only anthology-type shows can really dispose of them for a couple of weeks and say "that's fine!".
This is a pretty random damage roll on a large HP pool, I admit, but there's going to be damage, and it's certainly not purely "symbolic".