My dad still crosses thumbs. That's how he taught me.
However, I (totally on accident) ended up with the thumbs aligned pointing at the target that's advocated nowadays.
My thumbs just arn't long enough to cross.
Sg. Lumpy has it right. The proper grip (stance) is subjective. The various opinions on the subject are a good starting point and something to experiment with on the range, but none of them are definitive. The definitive in my book is "try this, this, that and this and wriggle around a bit till you find what suits you best."