I don't think the gulf is as significant as you're making it sound based on "30 seconds of googling". I had a pretty severe vitamin D deficiency a year or two ago and the (high-IU) prescription my doctor wrote for me was D2. I asked him if I could just buy OTC D3 pills and take more of them, and his response was "yea that's fine, if anything those are more bio-available".
This medical professional's nonchalance about the difference is in pretty stark contradiction to your bizarre claim that they "aren't doing even shallow research into nutrition". There's a million possible reasons they may have decided not to optimize solely for bio-availablility, just as my doctor did.
