Lately I've noticed posts with barely 10 points getting to HN frontpage. Was it always like this?

I believe it's the way the HN algorithm works. In order to give new and obscure posts a shot, it will add them to peoples feeds in their front page and see how they measure. Otherwise new posts wouldn't get seen and the flywheel would never get started.

So everyone acts as a sort of beta tester for obscure posts.

On weekends, yes. During the week, that’s also true if they arrive within a short time frame, e.g., three minutes. Almost no one looks at “New”. That is the real issue.

Maybe the algorithm has some kind of "momentum" to it, taking into consideration the velocity of upvotes.

Not as much competition on the weekend?

If you are looking to see the "true" HN frontpage (i.e. most upvoted posts), I'd recommend using https://hckrnews.com

I just assume bots

Bots doing what? How would the poster being a bot influence why the post itself makes it to the front page with just 10 points?

It’s about how quickly they get those points. It doesn’t have to be bots. Sending a post to friends with reputable human profiles, and asking for a vote kinda works of most social networks. Some social networks claim they have protection against this but I wouldn’t bet they catch everything.