Middle C is C3 in Steinberg Software, Yamaha also uses C3 as middle C. Not that this is related, Steinberg did that long before being acquired by Yamaha. Some software use C5 as middle C go figure.
Don’t expect that to ever change, most long time users would be extremely upset if it did (I would suspect) it is almost a religious thing for some. I don’t care personally, and would be fine if there was a option to freely change that, although I haven’t contemplated the consequences.