The Luchs, well, it was supposed to be amphibious. Turned out that not for all vehicles the PU foamed compartments were welded entirely watertight, so some of the vehicles drew an unknown amount of water during early exercises, which went fine until it didn't and people died, at which point all exercises involving swimming were stopped and the vehicle was cleared for amphibious water crossings "only in wartime".
Somehow trhe reason for this wasn't clearly communicated so all kinds of urban myths began to circulate, that the introduction of the thermal imager had made it top heavy, that the new run flat tires no longer provided the necessary buoyancy, that there had been additional armor plates mounted. But it was simply that full buoyancy from all foamed compartments could no longer be guaranteed - and it could not be adequately inspected and fixed either.
So, in Steel Beasts we err on the optimistic side, assuming that most vehicles were still capable of doing it.
At the end of the day I'm somewhat skeptical about the whole amphibious thing for armored vehicles. Reconciling buoyancy and armor protection is difficult enough, and then you haven't even answered the main question, how to get out of the water once that you're in. Suitable spots to get out of the water are rare. They usually need to be created by engineers, at which point the question must be asked if building a bridge really is that much more time consuming.
With large streams requiring the assembly of pontoon bridges amphibious/underwater driving capability may have some merit in selected spots but still the question is if it worth it, given the serious other compromises that need to be made at least with amphibious tanks.
The many dozen Sherman tanks that were supposed to swim to the shore on D Day that were located on the sea floor were all found to be oriented towards a certain church belltower, suggesting that they actually swam relatively well with their canvas boards, but were pulled into rough seas by sea drift, until the waves became so rough that they filled the inside. So, up to a point the design worked, but the drift wasn't taken into account by the release points, so my conclusion is that the compromises involved are so severe that you need very good reasons to seriously consider it.
Experiments with the Elbe-Seitenkanal in 1984 showed that there simply was no way how armored vehicles, swimming or driving under the water, could climb out of the canal again. Video in German: