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Some examples in various iOS apps:
US Bank
RentCafe 
Uber 
The first two kinda reminds me of the icon for aligning text justified left.
I'm quite curious about the reason for this change. I couldn't really find anything about it online. Could someone provide some insight and perhaps some online resources that talk about this?
I think there's no reason beyond the evolution of the design itself.
This is what I think about usability in terms of design:
Asymmetry: It's well known that asymmetry is perceptually more unsettling, thus offering greater visual impact.
Spaciousness: The hamburger menu is used more frequently on small screens where saving space is a fundamental premise. Although the width of the icon and the thickness of each line may be the same, the difference in the length of the lines gives the feeling of spaciousness to the area where it is located.
A simple test in Google image search:
