I also use a starting clamp to start my crosses, so all knots are the same,and you would not be tying off on a main string and pulling tension against it, and when using thin gut or other 'fragile' multifilament strings, and especially at higher tensions, it is not uncommon to snap that first cross string right at the knot or at the two sharp turns the string makes, With using a starting clamp, you do not pull tension against these turns. The USRSA stated at a stringers symposium that they will be updating their recommended procedure, for using the starting clamp use to start crosses.
I get rid of the starting clamp usually right in the beginning.
I clamp the end with the starting clamp outside the frame, then clamp the far end as usual(fixed clamps), then clamp the near end and get rid of the starting clamp and tie off right in the beginning, just so no accidents occur to knock off the starting clamp.(Obviously I wait till a few crosses are placed on racquets that tie off on crosses like the pure storm which is tied to the 3rd cross),I actually see no benefit to waiting till later, but I'm sure its a matter of preference like many other issues. ( Since that beginning cross string is now a tie off I also up the tension like I usually do for tie offs, but thats another issue) .