Is this token deprecated?

I notice that very few driver configs actually use it, when implementing
entitlements.

Regardless, I also notice in IDM 3.61 and 4.01 that the
<entitlement-impl> XML gets appended to the event document, even when
not using the token.

Is this token deprecated? I never really used it, so I was just
wondering. (AD Driver for example does not use it...)