Guess schema mixes columns returned by tck service

I have a connector with a List<String> Option binded to studio schema thanks to @Structure. The annotation is configured with a service name to retrieve schema columns:

The service generates 5 ordered columns :

The columns'order in the studio schema is not kept:

Each time we click on 'Guess schema' the order is changed. It can be very confusing for customer when the service returns hundreds of columns and then he wants to remove all except 2 or 3... Very difficult to retrieve the ones he wants to keep.