That sounds like it indeed rules out the aerial cartwheel as well as the butterfly since neither of them are flying kicks, but both appear in traditional boxing and weapon sets.
The fact is there are plenty of movements within traditional Shaolin sets that are "strictly gymnastic" to build the overall athleticism, agility, and flexibility of the practitioner.
For example, the Southern Courtyard (Nanyuan) Datongbiquan is a very traditional set which has a jump side split in it. It's certainly not there to kick two people simultaneously, or at least that's not a technique I would ever attempt...
I think these movements should be allowed if the competitor can prove they are originally part of an old boxing set, which shouldn't be too hard. There can't be a zixuan division in traditional forms competition anyway. If people are doing butterflies in Qixingquan they're obviously just throwing things in there and breaking the rules, but it is legitimately a part of other traditional sets.
Much of the decision then really depends on the experience/knowledge of the judges.