If you’re talking about people with the technical sophistication to consider software services based on their technical merits, then sure. Your average user couldn’t even tell you the first thing about which non-content-based criteria might inform a spam score… or have even heard of a spam score. So they will absolutely not blame Gmail if another provider’s email gets spam flagged… they’d probably just think “why don’t they just get a Gmail account,” à la iMessage users/green texts.