And rightly so.They do not have radars,so they would assume that they face 30-35k BB.Nobody hear about Yamato class BB in their times,after all.Good point. They would assume they have a speed edge over the Japanese ships and expect to be able to get away if they have to.
People usually see what they expect to see,they go for sailors,too.
Yamato is an outside context problem for the Kaiserliche Marine.
From their perspective upon seeing her at very long range based on what they know about the IJN: "She's probably a battlecruiser packing 6x15in in twin turrets or 9x14" in triples."
Until she's close enough for them to discern the number of guns per turret and get a rangefinder on her they'll be blissfully unaware that a) those aren't 14" or 15" and b) she's a whole heck of a lot bigger than anything they've got.
All true.Probably they would be unaware of reality till Yamato start firing.