https://w3c.github.io/push-api/#dom-pushmanager-subscribe does not mention whether a https://html.spec.whatwg.org/multipage/interaction.html#transient-activation check should be done.
AIUI, Chrome and Firefox enforce these checks and WebKit is about to add this check at https://bugs.webkit.org/attachment.cgi?id=455337&action=review.
Would it make sense to update the spec accordingly?