Scirra doesn't block links on other sites, only on their arcade. The reason you have to use a button is because then it counts as user initiated action, using browser object to automatically open links when clicking other objects/sprites within games is done to prevent games automatically opening new tabs. In other words it seems like clicking on objects other than buttons is like onLayoutStart opening a link, doesn't count as user initiated.
If other sites iFramed your game from scirra arcade and Scirra arcade blocks links, then maybe they would be blocked on all those sites. Not sure about that one.
Exporting from Construct 2/3 to scirra arcade may do something to links, again, not sure.
But yeah, I am not uploading any more games to Scirra arcade because of links being blocked. I don't see the point.