No it won't. An phone has around 5 watt hours. So: 5 watt hours / day * 150 million people * 365 days = 273GWh / year / 4,116 billion kilowatthours / year = 0.006651% of electrical usage.
Yah, it's virtue signaling, not anything real. And keep in mind 0.006651% is total electrical usage - this time shifting might save 10%, so actual savings are even less than that.
There are over a billion iPhones in use worldwide. This technology is also being brought to MacBooks (100 million+), Watches (100 million+), and iPads (150 million+).
Your fundamental numbers are staggeringly inaccurate.
And, most crucially, representing it as a whole of the electric usage instead of peak hours intentionally misses the point of reducing peak hour usage. It's called "peak hour" for a reason.
Getting data about peak hour usage is much harder, but I would wager it's at most as much of that. So yes, completely insignificant at a large scale.
If anything, the biggest impact will come to individual consumers, if and when electricity prices start varying more widely across times of day.
[0] https://www.iea.org/reports/electricity-information-overview...
That is the entire point of this exercise. My point is that OP fails to address that with data (as do you).
Based on the data we do have, there doesn't seem to be any reason to care about iPhone charging - so, if you don't come up with some data or rationale for why we should, then I still feel it's justified to say that this change has little chance of helping the world in all but the most minor of ways.
If 1W of gas fired power needs to be brought online in the middle of the night to charge your phone, then all the wind power gets the same price. That's why peaks have always been the most economical place to target investments.
It would be interesting to compare the charge rate of a Tesla Powerall * the number of them deployed. I can see iPhones alone winning that depending on some assumptions you make.
You'd then probably be able to find stats on what Tesla gets paid for providing that service to get some idea of scale.
You are the one making claims with poor data and assumptions, not me.