I’m all for that bikejames article.
I’m a BMXer, i approach bike selection from a handling viewpoint, not “fit” as such, fit in the saddle is an after thought.
AS I see it what separates trail/all mtn from xc is that it is based around being “technical” rather than getting your head down and churning out as many miles, as quick as possible.
Obviously trail riding is going to involve some miles in the saddle to reserve energy for the downs, but you can’t have you cake and eat it as it were, normally better fit in the saddle doesn’t mean better handling.
Also I know everyone wants to be a badass technical rider, but a lot of the time people are just xc riders too unfit for XC and lack technical ability, get trail/all mtn bikes then try to turn them into XC bikes which isn’t going to yield the best results.
I agree with the article that trail riding should involve more out of the saddle attacking than in the saddle plodding along, but fitness prevents that for most.
But it is all just bikes at the end of the day, there’s no rules, everyone should enjoy it in every which way they deem fit.
These are just ramblings, take it as you want.
OP – definitely get fitted on your road bike though.