I don’t think the types of relations as described above are a result from primarily text based conversation, but years of gaming with the other person until 3 a.m. and while doing so, being on Teamspeak, Discord and the like. Talking to the person really makes these connections much deeper. I once started using in-game voice chat and simply asked the person something, and just from hearing his “yes” I could tell he was the same nationality as I and could even pin down the region from his accent, so the conversation started and became quite interesting.

Not saying this can’t be happening through forums, but I’d say it’s less likely and slower.

The other difference is that there is some authentication. I generally don’t play with a mic and I have some “friends” I enjoy having very minimal text chat, but mostly because they are good players. I do t consider these significant because I don’t talk. If I did, they may be surprised I’m a middle age Aussie guy, up way too late playing with the US. The authentication that voice offers makes it far more personal.