I've decided when it comes to etiquette there is a hill I'm willing to die on - whether or not to have registration cards included in the bridal shower invites. My mom is hosting the shower, she wants them in, I don't. I told her to include our wedding website which lists it on there if people want it. As a non-computer literate person, she is not a fan of the idea. Granted in our acquaintances it is a common practice to put 'So-and-so is registered at XYZ" or include the registration cards. When, last year, on my cousins invite nothing was mentioned in the invite about the registry or where they were registered except their website - many family members were confused as to where to go to find out IF they indeed were registered, my mom being one of them. She called me and I looked online.
She's very generously hosting my shower. In the grand scheme of things, if she wants to include the registry card, I'm completely ok with it - it makes her happy on a day that she's doing her absolute hardest to make me happy. If people side-eye it I'm perfectly ok with that - for my mom and her peace of mind/happiness, I'll breech this etiquette. Side-eye away.
ETA: Updated after PPs thoughts - So glad this isn't a hill I need to die - I must've gotten it confused with not mentioning it/including the cards on the wedding invites (which I would never do). I'm pretty sure I'll need to save the 'hill to die on' for something later - so I'll keep it for now.