[MaxBarraclough]

> Responsible email publishers use lack of opens as a signal to reduce volume of emails sent and, eventually, unsubscribing you automatically.

No, they don't.

> Gmail causing a lot of bogus engagement would make it look like people can’t get enough of your content

For a few days, perhaps. Gmail accounts for a significant proportion of all email. 'Publishers' would quickly realise they are no longer able to track emails sent to Gmail. To fail to do so would be their loss; if that weren't the case, they wouldn't bother with tracking at all.