I'm sure from an engineering standpoint, the loops in endless strings are just as strong as the body of the string. But I question your contention that "having a loop twice as strong as the string has no value." Two reasons: 1) I've had many endless loop strings break, nearly ALWAYS in one loop or the other and only very rarely in the body. 2) Not one single flemish string has ever broken on one of my bows.

Now, it might be possible the reason for that is you can readily see when the loop is damaged with a flemish string while any damage to an endless loop is hidden under the serving. That's a visual indicator to tell you it's time to change the string. Or, when several strands are damaged in the loop, an endless string could be weakened enough to break while the extra strands in a flemish loop give you built in redundant safeguards to keep it from breaking.

Either way, there is a real, tangible value to flemish strings' stronger loops.