Update on this...
I ended up choosing the "do nothing yet" approach, figuring that as I used multiple different blades over the course of time I would learn more...
Interestingly, all these months later, all blades go on and off as easily as I would have expected based on previous experiences on other saws.
My only thought is that perhaps the arbor had received so few blade changes before I bought it (it was VERY lightly used when I purchased it) and had some minor burrs (although my bare hand could not detect them?) and they have since worn away during normal use.
Shrug... totally weird one, but all is well again now... and I guess I learned that, in rare cases, giving something like this a little more time to present additional data points is a decent strategy.