I bf until Dd was almost 10 months until around 18 months she was a pretty good sleeper, after that she turned into an early rising little bugger!
In my experience - not just Dd - but as someone who has cared for many babies fed in different ways (bf, Ff, combi feeding) it's nothing to do with how they're fed.
How they sleep is more to do with their personal ability to do/not do so.
My dd struggles to stay asleep even now (she's almost 20!) unless her room is totally pitch black! The slightest chink of light wakes her...but noise wise you could blow up a bomb next to her bed and she'd sleep through it
Plus to be honest I agree ff is a pita for night feeds if you're the one doing them.
My milk dried is why I stopped bf and had to switch to ff, and even though as per the advice then (and still ok to do now though more discouraged) I made up 24 hours of bottles in one go each evening, chilled quickly and refrigerated so in the night it was "only" a case of retrieving and heating bottle that still meant trailing downstairs, boiling a kettle (I heated bottles by placing in a jug of boiled water), waiting for the damn thing to heat up, then calming dd down enough to get her to take it!
Bf I didn't have to leave the bed most of the time
or at most only to retrieve dd from her cot/room past 6 months. And I could easily "doze" while she fed. Quicker and easier
So I too think it's possible ff mums MIGHT be woken fewer times but need to be awake for longer - which, I don't know about you but certainly for me, meant it was harder and took longer to get back to sleep too.
As for "research" saying ff babies sleep better
1 I'd be interested to know who funded that research. If eg it was nestle or similar hardly surprising
2 such research would be VERY dependent on subjects self reporting which is always questionable