You definitely get a war justification warning as the UK while Germany's taking the Demand Sudetenland focus, I've seen it many times.
In the case where I did not, Czechs did not exist as a country any longer. It's been a few years now. I was Poland, but I can't remember the exactly timing. It's possible that something like this happened:
- I declare on Czechs
- Germany takes demand Sudetenland before I capitulate them.
- I capitulate them before the focus completes.
All I know is that there was no "demand for Sudetenland"...the event didn't handle it like usual when Sudetenland is held by Poland. I was well acquainted with HOI 4 BS by this point, and I knew it was around Sudetenland time, so I was already set up in the forts (this approach to Poland made the war quite easy a few years back, as Germany thinned out its offensive substantially to cover Sudetenland, blunting its offensive). I figured I'd get attacked one way or another, but I definitely didn't get usual warning.
This was old Poland focus tree. Managed to win it May 1940, so USSR was screwed.
One might say "well you did something ahistorical", but that's an invalid response to the complaint. The game breaks when you involve special cases to rules w/o notice. A less experienced player might have guessed Sudetenland focus wasn't valid/bypassed, or at least expected to be notified if an attack was imminent, since that's what the game normally does (even in true historical surprise attack scenarios like Pearl Harbor). This player might then have suffered a significant setback due to developer mistake rather than their own mistakes. It's not good for the game.
Edit: funny to get random disagrees w/o discussion. I get it when I state preferences that are different to other posters, but this is simply showing concrete evidence to prove what I describe actually happened.
That a) I was declared on and b) the game gave no notification that a war goal was being created against me are
matters of objective fact. Also noteworthy that c) if you justify on a nation and it's conquered, you can't declare on the new nation normally, so this is also objectively an example of special casing breaking otherwise established rules. You might disagree on how important issues like this are (I consider them significant problems with how the rules are implemented), but that this stuff happens isn't a matter of opinion.