Not my PM (in the US). My PM would try to avoid anything that is not absolutely necessary and therefore ask developers not to develop anything that isn't a MUST. I know that we like making fun of Europe for their alleged lack of innovation but this isn't a Europe thing.

Implementing a 20 years old needed RFC header is the cutting edge of innovation

Your PM most definitely would not tell you to skip a feature that is needed for your emails to be delivered to Gmail accounts. What a preposterous thing to lie about.