Strom, there wasn't such a rule (or maybe more like policy) in force a few years ago. Maybe new or maybe been there all along but not enforced ... and must be due to all those numerous complaints about scantily dressed ladies in short shorts and figure hugging tank tops and the numerous counter arguments about freedom to wear whatever one likes. There were also allegations of sexual harassments happening, so it is always a double edged sword. While restrictive but the rule or policy is actually for the protection of women. From many expats' background, this is ridiculous and is totally a non-issue ... But the same does not apply for everyone.

In your case, you (and many others) were decently dressed and not in breach of cultural rules but usually the enforcement of any rule or policy has to be a blanket enforcement for ease of execution. However, IMHO, the authorities should allow some leeway for decently dressed ladies to enter the Aspire Park. It is a park, after all. However, having said that, it's not too bad to just put on a thin black abaya, not too hot and just a matter of getting used to wearing it.