Appreciate the responses, vjudeu, thank you.
Does help me to understand a bit more on the behaviour of nodes, and how Core isn't actually the Core I'm assuming (though for practical purposes probably they all do the same thing). And confirms somewhat my thoughts on Core being more dev than user friendly. Not sure that will ever change, though I feel it is important if we want to expand diversity in node operators too (or is it?).
Overall omewhat gives me a bit more context about the topic, though I feel still, I don't have quite enough to answer "why client diversity isn't an issue for Bitcoin"!
Does seem to further back the case or need for client diversity though, no? =)