E-mail was always asynchronous communication tool.
For people who like to see waving three dots in iPhone chat, e-mailing makes them anxious. So I understand that apology is quite normal.
It is a sort of generational difference, imho.
I took a day off texting to sleep and recover from an injury, and the woman I was seeing (in her 30s) threatened to delete our chat because she assume I was mad and ignoring her.
She's part of a certain digital generation, and expectations change.
A younger PM I'm working with right now emailed me twice in a few hours because I didn't immediately sign into their management platform after our 4pm meeting. Granted, that's her job, but the project doesn't officially start for a few more months.
> generational difference
I feel squeezed in the middle between antsy-verbose zoomer emailers and terse boomer emailers that hit me with ambiguous 5 word replies or those godforsaken emojii email reacts.
My decree is that 95% of emails should be three sentences double-spaced. 5% should be paragraphs. Hypertext is permissible almost entirely because of quote formatting, which should be used liberally so that each email is as self-contained as possible.
written letters are asynchronous but people expected timely (relative to snail mail) replies even back then.
Chats are ambiguous because it functions both as sync and async. I treat my whatsapp messages as async, but time and again I get heat from people because I take too long to reply, something I'll never feel the urge to apologize for.