Hitler's orders aren't a doctrine. If you are heavily invested in mobile warfare and yet find yourself on the defensive you should probably do what various German generals wanted to do, shorten your lines enough to free up mobile reserves able to launch counter-attacks or to cut off enemy spearheads that break through your lines, to play to your strengths. If you feel that you absolutely cannot give up any provinces you can try to hold a static line if you want, but like Hitler, you won't be playing to you army's strengths.
To better address the actual effect of said doctrine choices, we probably should see the benefits of unlocking these fancy icons on the trees. But as such I still disagree (to a point) based on historical grounds that concentrated superiority/firepower is mutually exclusive with blitzkrieg, in fact, it's a part of it, if we want to have a blanket name for what the germans did.
Also, if Hitler's orders override any doctrine, as a sort of an anti-doctrine they do act like a doctrine themselves.
And even if there would be this desperate defence as a last ditch attempt, it still leaves mobile/elastic defence out of equation. Any competent leader knows you might need to defend at some point, and would prepare for such eventualities. Players are not Hitler. Hopefully.
Thank you for the reply, btw. I do appreciate devs being up and about explaining stuff and design decisions!