The ice in that case might have helped with the temp issue. i've never tried, but I'd imagine it mitigates it at best.
Many times introductory instructions provide steps that advanced brewers might do differently simply because it can help make the process easy to explain/do, and the beer can still come out great tasting.
I personally like to improve my hobby wherever I can, so I avoid oxidation now, because I understand it's impact. That's why I'm on this great forum.
Can we please all agree that leeching plastics at high temps is not a healthy/wise choice, and that although you may not "notice" anything in your 1,000,000 batches that you are still putting yourself at longterm health risks? If you don't care about the long term health risks... then fine. And please don't respond with anything like "well, I drink beer and that's not healthy." Not a relevant point when we're talking about leeching plastic.
As for the pouring boiling wort (or wort over 90F for that matter) over ice, or into a bucket, the main concern there is oxidizing your wort.
Of course, you can still make great beer, I am not arguing that, but if there are simple steps you can take to avoid things like leeching plastic or oxidation, then it's certainly worth consideration.
hope this helps guys.