Published on 12, July, 2020
The guy in question is affectionate and initiates physical contact and intimacy a lot when we're together but only seems to struggle with maintaining communication in between meet ups, either through texts (often takes a long time to reply) and says he often gets quite mentally tired with phone calls or video calls
The answer to your question is I don't think he is struggling with communication, you just have different expectations over what/how much communication should occur.
If I am at work, I am immersed, so it does not occur to me to text anyone to 'check in' and say pointless stuff about how my day is going. I will tell you when I get home, or on our date. Also my employer is paying me to work, which the other person knows, so I would not text, as I would see it being dishonest use of work time. During my breaks I would be eating or rehydrating, on my own or with others, again it would not occur to me to send a (to me) pointless text to say I am having a cup of tea. I do not struggle with this, though I can see it would frustrate someone with different expectations.
I'm with Martin - once I trust the other person and they are a friend, they are friends for life (unless I discover they lie to me). I can go for days, weeks, years without contacting some people and pick up where we left off. I rarely read texts when they come in (I choose when I have energy to read them), as I am living real life not life on my phone.
Sometimes it takes me a couple of days to text back, as I have no energy to stew over the exact wording of a reply which answers your question, deals with all the inferences and nuances you imply but don't explicitly state, keeps my need for honesty but compromises by not wanting to say something you might interpret or infer as offensive or hurtful. There is no tone to a text, the reader adds that themselves, so I tie myself in knots finding the exact words... and the other person interprets it in a different way. That, I do struggle with.