The limit of 2 border entries using visa exempt entries no longer exists. The use of “unlimited” as a term is misleading in terms that there is no actual limit, but you won’t get away with “unlimited” entries. You will get away with as many as you can get away with until the immigration officer decides that you can’t anymore. Whether that is 2, 3 or 8 is up to them.
Different people will have different experiences. Some airlines will insist, some won’t care. The fact that you got in ok has no real relevance to others’ experiences
Actually there are visas obtained inside Thailand. The Non O based on being over 50 or married to a Thai are two examples. They are visas. They come with zero entries because you are already in Thailand, so you’d have to have a re-entry permit if you wanted to leave.