I don't think investing should be dumbed down to betting. The public already has high aversion towards "throwing $120K at [random] companies". YC (and with them a lot of accelerators/investors) analyze their prospects.
Sure, sometimes there is a chance and an underbelly-feeling involved in whether a startup should be invested in, but to degrade investments as "betting" is probably the highest insult an investment/accelerator-firm can get.
The parent's suggestion is that to refer to a YC investment as a "bet" is a little bit of a misnomer. It's a targeted, reasoned investment, not "120K on 'Little Devil' to win."
Sure, sometimes there is a chance and an underbelly-feeling involved in whether a startup should be invested in, but to degrade investments as "betting" is probably the highest insult an investment/accelerator-firm can get.