Nope.
You just don't understand sporting rivalries.
Jeremy - you do understand that one of the aspects of the Welsh rivalry with England is that they are obsessed with winning the world cup.
Frankly there is nothing about the history of Wales vs England that can justifiably stand out against the other - victories, much of a muchness, 5/6 nations victories etc - much of a muchness. Except for one thing - the biggest of them all. England have won the world cup and Wales haven't. This rankles more than any number of 6 nations victories, as none of them can change the easy retort - 'well we've won the world cup, how about you'.
There is also a common grump that Wales' 'great' period (the late 1960s and 1970s) was before the world cup started with a view that had the world cup been in existence then that Wales would have won it multiple times (that is of course pure speculation and unlikely to have happened as they still were unable to beat New Zealand, even then).
Point being that a key part of the Wales rugby psyche is that they will alway suffer from a huge 'chip on their shoulder' until they win the world cup. Nothing else - any number of 6 nations grand slams including victories over England will change that. And regardless of a useful local rivalry, the real rivalry is with New Zealand - the team they couldn't beat in their pomp (or since) - the country that is like Wales in so many ways and the only other country that can claim rugby to be the nation sport with any kind of justification.
The true dream for Wales fans is a world cup final victory over New Zealand.