testing requires a large number of diffrent hardware combinations and a lot of  people spening a lot of time  operating these… a tiny studio might struggle to pump those testing manhours into a patch, with people  at their front door frothing at the mouth, demanding immediate release of patches, and already ighting torches.
Also, the release date is not a thing you can just adjust a week before release, there is quite some time befre when the machinery in the background begins to work its magic. and with a publisher (deep silver) even before the “point of no return” the devs are not on their own to change the date, but have to agree with the publishers, which usually have rather tight control over it. The publishers  notoriously care little for the products state or quality, and have quarterly reports etc. to worship, and  tend to stick to their dates at the detriment of many a game in recent past.
At some point, there is very very likely no option to change the release date anymore, and when (as usual with many project, especially when you are new in the trade or a new company) towards the end stuff  begins to fall apart that previously worked, you can only ever hope to brace fir impact and duct tape and WD40 together as much as you can of the game, before it ships…
To either abandon it shortly after, or stick with it, and try your best to  get it to work.
WH appears (so far) to try to fix it, though it seems a rough path ahead.
I hope they stick to it long enought o get it to work for  the veast majority of people, and to learn important lessons on processes and practises, so their next dlc or game will turn out better.