If it turns out they can't, would you not be surprised if that was the case though?
With that said, like you are saying, I don't think we can slam down the hammer and says it will be that case (J15-b and J-XY/35 compatible with both STOBAR and CATOBAR).
But I think we can say it's a high likelihood/expectation.
I think the likelihood of it happening is higher than it not happening.... But I also wouldn't say it is "basically confirmed" -- which is the threshold where an outcome is so virtually guaranteed that it would take evidence to convince us otherwise.
The reason I'm harping on about confirmation and verification, is that the ability of J-XY/35 and J-15B to be STOBAR launched will greatly influence the future relevance and shelf life of CV-16/17, in turn greatly influencing the assessment and estimates of the PLANs overall projected carrier capability for at least the foreseeable future.
Is the J-XY/35 and J-15B's capability to launch from both STOBAR and CATOBAR "basically confirmed" or "all but guaranteed"?
I personally don't think so. Yes, the likelihood is high, but it is not "basically confirmed" or "all but guaranteed".
So by extension, it means we should be obliged to await confirmation and/or other forms of verification.