Former Hatter here (Solution Architect Q2 '21 -> Q4 '22). Other than the discussions that took place around moving the storage/business products and teams under IBM (and the recently announcement transfer of middleware), I wouldn't have expected engineering to do that much interfacing with IBM. At most, division leadership maybe (this is just personal speculation). Finance and Sales on the other hand... quite a bit more.
We had a really fun time where the classic s-word was thrown around... "s y n e r g y". Some of the folks I got to meet across the aisle had a pretty strong pre-2010 mindset. Even around opinions of the acquisition, thinking it was just another case of SOP for the business and we'd be fully integrated Soon™.
They key thing people need to remember about the Red Hat acquisition is that it was purely for expertise and personnel. Red Hat has no (or very little) IP. It's not like IBM was snatching them up to take advantage of patents or whatnot. It's in their best interest to do as little as possible to poke the bear that is RH engineering because if there was ever a large scale exodus, IBM would be holding the worlds largest $34B sack of excrement we've seen. All of the value in the acquisition is the engineering talent and customer relationships Red Hat has, not the products themselves. The power of open source development!
It's heartening to hear that your experience in engineering has been positive (or neutral?) so far. Sales saw some massive churn because that's an area IBM did have a heavier impact in. There were some fairly ridiculous expectations set for year-over-year, completely dismissing previous results and obvious upcoming trends. Lost a lot of good reps over that...