Imagine an extreme example of this. A person with a 30 inch draw length, such as myself, shooting a bow that is set to a draw length of 24 inches and me installing a 6" long loop to make up the differance. Yeah my hand may be anchored in the correct spot but you could hardly say that my bow is set up to fit me perfectly and my shooting will not be its best.
Absolutely correct. BUT... for those like myself who shot "off the string" for years before trying a loop may find the need to drop down a half-inch to accomodate the added length of the loop thrown into the mix. As I mention in my "how-to" thread on d-loops, today's "shorty" release heads help keep that draw-length loss to a minimum for sure though.
In other words, if I'm a 29" draw length when shooting off the string, and now add a d-loop that -- even as short as I tie them -- It will movemy anchor point BACK at least 3/8 of an inch
ifI keep everything else the same.