Hi Chris, Being the owner (and obviously biased), I think this one's more for me - the Tohachi attribution is backed up by recent Hozon papers directly to Tohachi and when you examine it in hand, there's really little doubt that this is a correct attribution, albeit not an obvious one.
The seppadai, when you look at it straight down, is correct for Tohachi, I can easily find references with the same seppadai shape. The hitsu-ana in this case are part of the rope design and can't really be taken into the equation - otherwise they're indeed a-typical.
And about copying designs - this exact design is also noted in the Kamiyoshi Tsuba Ehon, which makes it less likely to be a copy by another school, seeing those usually add their own take on a design.