Looking at the schedule for most direct, no-change, connections between Berlin and Munich, I do not find many (any) going through what I call a "stub" bahnhöfe, a station where the train come in on a dead end track, then goes back out in the opposite direction, changing the direction of the cars. Nevertheless, you don't know everywhere that coach has already been, whether the direction has changes before you get on.
So, I don't think you can count on the car map on the bahn. All it shows is the seat number, not which direction the car will be going, which seats are forward and rearward facing.
Now, I have not, due to my late partners health, Covid, and now my cancer diagnosis, been able to travel in Germany recently. But when I was last there, in the last 20 years, I took high speed trains (the only ones with reservations) about a dozen times. I can only remember one that was standing-room-only. On most of those trains there were a lot of open, unreserved seats, so there were always free seats to move into.
So, even if your reserved seats aren't facing in the direction you want, you can probably find seats facing the direction you want.
In 2001, on December 26, The Second-Day-of-Christmas, a popular travel holiday, my wife and I were on an ICE from FRA Fern to Karlsruhe. The train was crowded, every seat was occupied, but only a few were reserved. When the train got to Mannheim, a lot of people got up to get off, and, before new people came on board, we were able to find empty, unreserved seats to Karlsruhe.
Two years later I came back and took the same ICE from FRA to Karlsruhe. When I bought my ticket at the FRA Fernbahnhof, I asked the desk agent if I should get a reservation. He coyly answered, "You can if you want to". I thought that sounded too coy, so I didn't buy a reservation. I was one of four people in that coach, so I had my choice of seats.
So, depending on the train and the day, you might find that finding two unreserved, unoccupied, forward facing seats is not that difficult.