[WorldMaker]

Most text message apps have real time read receipts for A and "actively writing" indicators that imply some of B. (The things that we invented for "instant messaging" decades ago are finally mostly back in vogue in text messaging.) Text messages have "reactions" like Thumbs Up that very quickly say "I will action this shortly." For me that's more TCP, the classic ACK receipt then action.

A 15 second phone call probably goes straight to my voicemail and there's no read receipts if I have read the voicemail transcription yet, much less tried to listen to it. It might be hours until I'm in a quiet enough space to try to listen to it, because I don't carry headphones with me most of the time, don't listen to speakerphone in public, and the "phone speaker" on an iPhone is generally hard to hear for me, no matter how I awkwardly position the phone. The transcriptions are usually not good enough to action directly so I do usually need to do that dance of find a way to listen to it. Calls to me are a UDP hole with fewer acknowledgements and a lot of inconvenience.

Unless you've prescheduled a call with me, in which case maybe I do answer and maybe it is quick enough to be a 15 second phone call. But the easiest way to schedule that call with me is going to be to text me "Hey can I call in an hour about X?" and I'll ACK it soon after, and probably then likely spend 45 minutes looking for a quiet place to take a private phone call.

But, yeah, different perspectives for different sorts of people. Phone calls are taxing to me and the real world is a loud place and I don't carry headphones and I like to control the environment in which I try to answer a phone call, but also I find finding such quiet environments stressful enough to want to schedule them ahead of time.