I clicked through to odyssey's website and found the Japan tour, and looked at their list of Tour Directors. They appear to all have Japanese names. I can't be sure just by their names, but it seems a reasonable guess that the tour directors are all Japanese nationals, that meet up with the tour, rather than Americans or other nationals that go to Japan with the group. If it was the latter I was going to convince myself that it's not completely out of line to tip.

Given that they are locals, and they are doing business in Japan, I would guess that is is illegal for Odyssey to pay them less than a regular full time wage, the way tipped jobs work in the US. I hope someone with more knowledge of Japanese business/labor law can chime in on that.

It seems quite likely that Odyssey pays them a reasonable wage, but tries to make themselves an attractive employer by augmenting salaries on the backs of their customers. Personally, if it was me, and I got a request to add tips to a tour in a non-tipping country,_after_ signing up to the point of cancellation penalties, I would feel ripped off and bait/switched, and would be sorely tempted to refuse to tip just on that basis alone, even putting aside the impact that it has on local culture, which seems unwanted by the locals.

I feel like there's a 50/50 chance between lazy copy editing by Odyssey; and borderline shady business practices.

OP it is your call in the end, and I won't cast a judgment, but I did want to share my read on it.