To clarify, I'm not really concerned if they display supersonic feats after the FTL feat, the problem would be if they took a great amount of effort. That's why I noted Susie already blocking supersonic feats at the very beginning mitigates my concern around them.
Additionally, looking at the verse calc page, they already have several feats above supersonic, often
hypersonic and yeah the high hypersonic feat you mentioned.
I'm not getting the impression at all that they cap at those speeds, rather just consistently have super fast speeds.