Sounds like someone found a way to solve a problem that is not so easy to handle.
https://community.claris.com/en/s/question/0D50H000080CAauSAG/playing-with-cards-in-webdirect
Note: I'm simply sharing, I did not have that specific issue not did I try to replicate the problem or implement the workaround for it.
Web is a different animal. With regular apps, there is a constant communication between the user and the app.
But with Web apps it's different. I learn that while developing a Web app with Xojo. I wanted to use a progress bar so at the beginning of a method - similar to a script in FileMaker - I was bringing on the progress bar, doing the work and turning off the progress bar at the end. Result: no progress bar seen ?!?! That was because the app was not pushing the html to the browser until the return at the end was hit. There is no immediate communication in Web apps. That'S the way it is, and FileMaker has to do with it.