Tire threads...so much fun.
The bottom line is some tires work better for some riders on some bikes under certain conditions/roads for any number of reasons than others. A glowing endorsement from either a world class racer or weekend outlaw cruiser are equally unreliable in terms of picking the right tire for you.
I am currently riding on a brand of tire I swore off years ago, and find this particular tire from that brand to be the best I've had on the bike they're on. Lesson: keep an open mind.
I find certain brands typically "feel" a certain way on any bike I ride, and in my case, Bridgestones always feel like they are gliding, not gripping, and don't inspire confidence, whereas Dunlops always give me a strong grippy feeling. But I have good expereinces with Avon, and Metzler, and Michelin as well, depending on the tire model, and bike...so many variables. Lesson: experience will inform you better than other riders.
One needs to try several brands and profiles and pressures etc over the years/miles or ownership, which isn't hard to do considering a set usually lasts a season.
So yes, it's both, you and the tires re rear wheel sliding/locking-up under braking. Try some different settings, *including suspension settings*, maybe you're too "soft" in front, maybe too little rebound/too much pre-load in rear, etc. and if not happy, try something else next time.
And for heaven's sake, DO NOT stop using your rear brake. Learn how and when to "modulate" it.
This is my expert opinion.