there is a little bitty difference in the race to the bottom. you do not pass code and collect $200 mixing and matching the parts in the entrance panel. they are rated for service with a certain class of breakers, which are rated for a certain class of panel.
it might fit, but you are stomping on the codebook if you put a Siemens breaker in an Eaton BR panel. you need to stay within the brand, and within the series. don't know if a CR breaker will fit in a BR panel, but they don't belong together. the plating is different, they are not tested together, etc. (CR panels have a plated copper bus bar set, BRs are aluminum, for instance.) the inspector is required to drop their pen and frown. theoretically the "universal bus" is just that, but there are little physical differences that make the slippery switch obvious for a reason.
if you don't know if Schneider Square-D tests their AFCIs in an RF field, or Siemens, or Billy Joe's Gently Used Old Electrics, or whomever, you kinda need to ask around. so far, all we know about is Eaton working with the League. for 690,000 potential customers, at least, I think Eaton buddied up for a reason. it sure isn't costing them much to detail an engineer and poke about in the lab, over and above chasing field complaints.
this is why I asked way back when what series of panel was being dealt with.