Yeah, this person is acting like breaking their concentration on something, to read an e-mail, is drastically different than doing the same thing, for a text. This is a ridiculous assertion. Unless you intentionally make it so you have to log into your e-mail every time you want to use it, but just leave slack, or whatever, open. If you do, that is your fault, not something wrong with e-mail. You can just see e-mail notifications, and then look at the window, just like any messaging system.
This person just has an irrational, personal, dislike of e-mail vs other communication methods. They are trying to make it seem like they have some sort of objective reason for their preference, and it isn’t just a personal preference. This way they can try and force everyone around them to bend to their preferences, while telling themselves it is everyone else who is wrong. Like yeah, e-mail isn’t the greatest thing around, however it still has some aspects that it does better than anything else, especially in a professional environment. There are rational, objective, reasons most companies still use e-mail, even though they all have slack groups too.
All communication is a massive, productivity destroying distraction when you’re working on something.
Structured tools are designed to organize and control communication into channels that are designed to handle when and how you deal with different things. Email is not, and bad tooling doesn’t come close to closing the gap.
He’s throwing a tantrum over the perfectly reasonable “we have structured communication tools; email is not a legitimate way to contact me”, and pretending forcing them to use an alternate, bad tool is somehow doing them a favor.