First of all, no one needs to "justify" anything. We're all free to do what we want. I think it's important to speak clearly about these topics to avoid confusion.
And it is common practice, to free climb trees, or poles, provided the climber maintains a minimum of three points of contact. Two hands, two feet is four. You can remove one of these, and maintain three. You can use a lineman's belt to count for two (each hip), to allow you to work hands free. If at any point while you're climbing, you'll drop below three points of contact, industry standards require tie off with rated equipment.
Climbing rope, using a lifeline, or moving a tether up as you ascend all negate the need for a lineman's belt, sort of. If you introduce slack, or have the potential to introduce slack into any of those systems, industry standard has you using a second positioning lanyard (lineman's), to prevent you from falling, or back up your connection.
I would venture to say 98-99% of hunters until ten years ago have free climbed to get in a tree. With the advent of the lifeline, I think that number is probably closer to 95% now, but still overwhelming majority. It doesn't make it right or wrong. But there's millions of folks climbing trees with spurs or bolts, with only a lineman's belt. How? 3 points of contact.