Here's an interesting development. New banned and restricted announcement just added this:
https://magic.wizards.com/en/articles/archive/news/june-1-2020-banned-and-restricted-announcement
The companion isn't always available to be cast anymore, you actually have to take a tempo hit to do it. Don't know if it is enough, but it certainly makes it less "for free".
New Companion Rule:
Once per game, any time you could cast a sorcery (during your main phase when the stack is empty), you can pay 3 generic mana to put your companion from your sideboard into your hand. This is a special action, not an activated ability.
https://magic.wizards.com/en/articles/archive/news/june-1-2020-banned-and-restricted-announcement
The companion isn't always available to be cast anymore, you actually have to take a tempo hit to do it. Don't know if it is enough, but it certainly makes it less "for free".