Speculation: I think the phrase "new storage requirements that increase cost and complexity" points to the root of the line taken in this blog post: an aversion to SAN storage. I suspect whoever wrote it understands exactly what HA is and how it works.
Since Exchange 2007, the team's been agressive about driving down storage costs to increase user mailbox capacity - which is a good thing. However it seemed at the time that the Exchange team was trying to prove a point and some totally lost the plot saying "SAN is bad" or "we don't care if you already have one, replace it." Things have mellowed a bit since then.
I think that thread still runs through this response, it smacks of "we don't like what you're doing because it *requires* a SAN, therefore we won't allow or promote it."
Technical objections? Possibly, but none made public. Spiteful? I think so.