When can the baby sit in a high chair?

According to what I could find it's recommended against before age of 6 months unless the baby sits up by himself.

Our baby is 10 weeks and steadily sits up when we hold him (like we hold him almost flat but he does a full situp on our lap by himself)

He also has a recliner where he lays down on, which is slightly raised in the back so he has more visual and no reflux, he also does full situps on that.

Does that mean he is autonomously sitting up and is allowed in a high chair or not?

He doesn't roll yet or crawl or actually goes from laying flat to sitting, just the situps...