Sure. It can be "less" secure from a procedural perspective because it increases the complexity of the user accessing their info. The more difficult/complicated it is for the user, the more likely of user mistakes exposing their accounts in one way or another. Obviously there are password apps that allow for seamless login (some of those can also be problematic), which alleviates the complexity, but then you have multiple email accounts to manage on some level for the various services and websites you use.

End of day, if it works, it works, but it's important to pay attention to your user experience while also taking in to account the various tools (strong pass, mfa, etc) when setting yourself up. If you get annoyed that you have too many emails to manage, you might be more likely to not log out, or not use mfa, etc.

edit wasn't trying to say it was WAY more insecure to use separate emails, just that it probably wasn't necessary if you have different pass and use mfa. Sometimes 'more, better' isn't 'more-better'.