Clearly they don't want to repeat radeon VII mistakes. Launch day reviews will stick with radeon VII forever, even though we know now it's a much better card than people probably think yet it will always, in most peoples eyes, only ever be as good as those reviews. To show Zen 2 in it's absolute best light it needs everything intel has and more, pci-e 4 needs to be there, thunderbolt, insane memory frequencies, it all needs to be there and it needs to be working. This thing needs to come out of the gate and be everything everybody is expecting it to be. Ask yourself this, if you made a revolutionary product that you know to show in the best light needed a little time, would you execute anyway? Live with those bad reviews but know it will get faster in a few months or would you wait, get the chipset ready and show your very strongest hand?
To me this is where the scales start to tip. AMD need a clear winner, something that beats everything from the competition in every single metric both price and performance, a product that they can stand on stage and say "come at me", something that gives the consumer absolutely no reason to invest in the competition. The fact of the matter is that to really do that they might need the extra bandwidth supplied by the chipset along with extra memory speeds as well as any other secret sauce they are putting into the Zen 2 chipset, which they are developing in house (I really like this from a security standpoint to be fair).
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