But that's the point. This process is "faster" on a higher salary if and only if your final target income isn't also higher. For many people this will not be the case, e.g. the person with a 100k/yr salary has a higher retirement cost of living targeted than the person with 50k/yr salary does.
Of course, if you are happy living a 50k/yr lifestyle and retirement but happen to make 100k/yr, yes, you should be able to retire much faster.
The MMM lifestyle is something like 25-30k to live.
If you make 50k.. you can save at most 20-25k, taking (10-15 years to retire, would need to do math).
if you make 200k, you can save 150-175k, reaching retirement in 2-3 years.
The "higher income -> higher lifestyle" is a myth MMM tries hard to dispel. You don't NEED newer cars because you make more money. You don't NEED a bigger house. Sure you can choose those things...
It has a huge impact if you are willing to approach it that way, but my point is that I don't believe many/most people in that 100k+ earning range actually are willing to retire to a 20/25k range, at all.
Which leads you back to scaling everything up to the number you are willing to you are comfortable with.
Of course, if you are happy living a 50k/yr lifestyle and retirement but happen to make 100k/yr, yes, you should be able to retire much faster.