Could be, but...
The majority of strings I've come accross are not measured properly. This causes a huge problem with dacron strings. Most of them aren't pre-stretched either, which further complicates things.
Take that 64" AMO string you have (I'm assuming that's what you mean by putting an 64" string on a 64" bow). If it's dacron and measures 61" when it's not on the bow, it's NOT a 64" AMO string. Strings are properly measured under tension and depending on who made the string and the strand count, a 64" AMO string made of dacron is going to measure 60-60.5" while at rest. Under tension it'll be 61".
Measuring strings under tension, like they're supposed to be measured, makes a lot of issues in ordering strings be non-issues. You should be able to order a mixed batch of flemish and endless loops strings (12 strand dacron, 18 strand dacron, 18 strand FF and 8 strand FF, etc) all the same length for a bow and they should all brace the bow the same (ie measure the same length under tension while on the bow). At rest they'll all be different lengths, but if the string maker is worth his/her salt you only need to order the one length.
I'll get off my soapbox and go have a cup of coffee now. Don't get me started on bowyers marking their bows "AMO" when they're NOT!! :rolleyes: