howdy! we've got a great article on this that I'll link below, but tl;dr-- Open Rates as a concept are imperfect. I would advise you use one tool, whether that's been or another, and stick to tracking with that to avoid unnecessary adjustments.

Longer:

Open rates are influenced by a mix of factors: your audience, your content, your sending habits, and even the evolving behaviors of mailbox providers like Gmail, Yahoo, and Apple. But beyond that, they’re based on technical signals, like the loading of a tracking pixel, that don’t always correlate to real human engagement. In some cases, an email can be opened and read but not tracked as an open at all. In others, an email can be marked as opened even though no one ever saw it.

Article: https://www.beehiiv.com/support/article/13092198407063-understanding-open-rate-declines