While clearly not big enough to be able to sell a phone like the mini, there certainly is quite a vocal group of people who want less cumbersome phones.
Assuming this rumor is even close to correct and the iPhone really does shrink from the current 8.3 MM thin down to 5.5 or even 6MM thin with an aluminum build, the difference will be absolutely noticeable.
Even Apple‘s largest screen iPhones have still significantly increased in weight over the past 10 years, the 6+ was 172G heavy at 7.1MM while the 14 Pro Max was 240G heavy. Not just a little bit heavier, 30% heavier.
Given that this iPhone could be almost 2MM thinner than even the 6+, we could be talking about an iPhone around the same weight as the SE3 which is 144G heavy.
A phone that was only 150G but with a 6.6 inch screen will feel even lighter, just because of the weight to body ratio. And because of the single camera, the weight distribution will be more even throughout the phone.
I’ll bet you the weight savings alone will make a huge difference. I would not even be surprised to see plenty of 12 and 13 Mini owners reluctantly upgrade just because of how light and small the phone will feel despite the massive screen.
Edit: the 13Mini was 140G. So a 6.6 inch iPhone possibly within 10-20G of the Mini.
If even close to accurate, this thing won’t feel real. Well… until you put a case on it, but even then it’ll feel more like a large iPod touch. And the iPod Touch was tiny.