Did you find that your readers were generally more pleased with all books being available at once? (However that could be measured :D)
I got paid sales for books 2 and 3 very quickly, so some folks might have purchased the whole trilogy at once, but it's possible those were just fast readers who zipped through book 1 and then immediately bought the next one.
When I had my Bookbub, a number of folks bought all three books on the same day, but I expect that's just them having enough faith in Bookbub to merit doing that. I'm not sure that would translate to ordinary sales.
All that is a long way of saying I don't really know.

I know some readers won't touch a series until it's complete, though, so there's definitely a price to be paid for not finishing the series before publishing book one. I was aware of this back then, and I made my decision to publish the whole trilogy at once, and I don't regret that decision.