The first week or so of flower (all strains differ) most strains stretch, scroggers use this time to fill any remaining space in the screen but also to keep from having tall towering stretchy colas, and an even canopy. The stretch however can also be useful depending on what goals you are trying to accomplish with screening, or what environmental conditions you may be juggling etc. Space between colas and bud sites helps with air movement and keeps down "the issues associated" ie. molds/mildew.
Learning the plant always helps. GL.
Woodsmantoker~