Des made a couple Olympic Teams....she's obviously great.
As a teammate of her at Hansons when that first happened (and when she got 2nd at Boston),
I would say it is fair to say if we had "super shoes" back in 2011-2012 we probably all would have been 1-3 minutes faster for a marathon. Maybe not 100% as some respond differently, but some super shoes are for sure making people (Even elites!) a few minutes faster. The science is clear on that.
As far as "legal courses" go....well, people like to discredit anyone's PR nowadays if it doesn't show up on their World Athletics Profile. I believe times/performances need to be taken into context:
Following only World Athletics, that basically means none of you can count your PR from a course like CIM, Boston, Grandmas (or in my case Rock n' Rock San Diego) either then.
But the issue with Des is that her fastest time was not so much the net downhill nature of the course (Boston)...it was more the fact that on a point-to point course you have a potential for a massive tailwind. And that's exactly what happened when she ran 2:22 there for 2nd in 2011 (remember Ryan Hall ran 2:04 in that race too?!).
Then of course when she won Boston it was a super headwind day (tough conditions!). So there's that performance also....despite the relatively slow time. It could be argued that she does really well on extreme weather days at Boston.
But I would agree there is nothing from her 5km, 10k, and half marathon PRs to suggest that she actually was a "sub 2:20" kind of runner on a flat course in normal weather conditions....even if she had super shoes back then. However, if she had super shoes on that day at Boston her time very well could have been 2:19:xx....just everyone would have also been faster and she might not have gotten 2nd then!
Our cohort is a tough one to be in though...because I look back at my prime marathon years (circa 2011-2015) and think "if only those super shoes were out back then!"... Runners drop 2:18 like it's nothing now. These are runners that used to run 2:21 before!