We are migrating to 7.3 and I just want to check if Appian recommends using the

I would suggest you work on ways to get around javascript logic on forms where possible (chaining will be broken on any non-tempo-enabled forms, and you won't be allowed to tempo-enable forms when they contain javascript, so yes). But the use case you describe could probably be handled by post-form validation...

I would suggest you work on ways to get around javascript logic on forms where possible (chaining will be broken on any non-tempo-enabled forms, and you won't be allowed to tempo-enable forms when they contain javascript, so yes). But the use case you describe could probably be handled by post-form validation...