It's referring to the version when this class was originally introduced as JToolbarHelper. It was moved to a namespace in 3.9.

It's a valid concern though.

@SharkyKZ Thanks.
Though JToolbarHelper and ToolbarHelper are different classes.

We didn't choose to change the since tags when we namespaced all our classes - as they are a class_alias they are actually the same class ;) . Other than that they largely should be good - although occasionally people have copy/paste errors.

Yes, but you can't use namespaced classes on 1.5 even though @since tag says it was available in that version. Very misleading.

Other than that they largely should be good - although occasionally people have copy/paste errors.

It is good when the alias is used. If a developer decides to use the namespaced class, has no clue about it's introduction date/version in Joomla.

It still is true that the namespaced class can't have a "since 1.5", because it didn't exist in 1.5.
The purpose of that tag is to show in which version that element (class) became available.

You could try to add a since tag to the alias (don't know if that is possible), there it would be correct. But not for the namespaced class.

I would say close this issue - no one in their right mind is going to visit each and every since tag and ensure its credibility and update the wrong ones now.

Maintainers see above - can't see this ever going to be changed so no point in it being kept open

It still is true that the namespaced class can't have a "since 1.5", because it didn't exist in 1.5.
The purpose of that tag is to show in which version that element (class) became available.