1) I was speaking personally, for myself. Note the profligate use of the pronoun, 'I', in my post.
2) Read some of the Roger / Lensrentals blog posts about some of the messed up stuff that happens to some of their rental gear. If you'd honestly be happy buying something that had been used by a succession of people as a tool they didn't own and weren't planning to keep or use again, even at a discount, then putting the rental price* toward the purchase price might make sense for you. It's not likely to be a 'pristine, but used' copy you'll be buying from Lensrentals. I would not do it, any more than I'd buy a used rental car from Hertz or Rent-A-Wreck.
* note that the fine print of the offer is 'take up to 7 days of rental fees off the purchase price,' and in my case, I specifically mentioned a 3-week rental, meaning I'd only get 33% of the rental+shipping fees I'd paid applied to the purchase price, in the above example. If you're going to talk about facts and not ignoring them, at least please try to get the facts correct.