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think the older lengths (around 250-350 yards) were more accurate....a couple of the newer lengths had them around 700+ which is way longer than they actually were....

I found the same thing but in reverse on my 21 day solo trip route. Before I went, I looked the portages over and compared the new Chrismar with my old McKenzie's and when they disagreed, I went to the new Q-planner site.

That only made things worse because it varied between the two.
When they were ALL off, it was by a lot, more than you'd think it would be even allowing for minor human error.

One of my goals next trip to to bring a pedometer and mark each portage length down and then put any differences in my trip report.

On one hand, for me the length doesn't matter because if that what it takes to go where I want, I'm doing it regardless. But some people/groups have time/physical issues and a portage that is way longer than marked could be an issue for them?