HAHA. You posted the question but don't like the answers. That's rich.
I'm on the same page as Shel_B and Capriracer. I try if at all possible to keep the same all around. I've experienced the different treads etc but with the snow tires and all season. For my families safety I now keep it matched. I have used take off almost brand new tires.
Your "waste of money" is his and others piece of mind. Great country to spend ones own income on what they like between needs, wants, habits, happiness. Do you ever buy coffee from Starbucks, 7-11, Dunkin'? Why not make it at home and not waste that money. Bottle water/tap water etc. list is endless. Why fill up your tank before storms when you have enough to get to work and back and can stop daily. That extra weight from the 10+ gallons takes away fuel economy.
I have sold my used tires that have plenty of tread (for others) and still a decent date code. I have donated some to used tire places to help those that maybe can't afford to get new all 4 matching. I gave a set of 4 that I was going to sell to a co-worker with sidewall blowout (on 10+ year old tires) that was short of cash.
He didn't ask your thoughts on if he should buy matching 2 if 1 not available. He just said what his plan was and that involved a full size spare which he was planning anyway. You decided it was a waste of his money, he asked what you benefit you get by using mixed treads on different sides, you didn't like the questions/answers....That's rich.
OK That's my rant for now.