"Managed $XX,XXX site redesign that resulted in [cherry-picked numbers to make it look like it improved things when it didn't at all]" looks good on a résumé.

Your managers may not understand much, but they can understand (by which I mean get a thrill out of looking at) before-and-after screenshots on a powerpoint, which may matter when promotions are available.

That's at least as true in bigco as in startups and small companies.

But these kinds of mistakes can kill an early stage startup.