They should allow smart cargo shorts and jean shorts, or any knee length type that go well with a shirt. I don't get why there has to be such a strict dress code, it costs enough, leave it at "dress code: casual smart(no trackies etc)" and let them in. That's probably toffee-nosed Karens(not you kaz) complaining about "rif raff" being allowed into "their section".
That said, I wouldn't blame the whole club for one jobsworth, with no common sense. Also, at least you've a funny story to tell now, to your match going mates.