Good points & thinking.
So, a chemical like clethodim needs more surface area. Thus not mowing is wise as more area for grass to absorb chemical. Plus it’s slow acting & takes while to get into roots. Also why adding crop oil important + higher water volume…. For more surface exposure & thus more plant intake.
Gly is a bit different. In short, where gly is most effective is on: the most actively growing plants. …. Right after mowing when a plant starts to shoot up new green growth & regenerate. Or for grasses, in the reproduction phase when it’s starting seed creation process OR while it’s growing in length at rapid rates far from full maturity. Smaller plants with less area are easier to disrupt & stop photosynthesis- killing the plant easier.
When its least effective is when the plant is clearly not growing or growing the least. Let’s say a “mature grass plant”…. That’s the absolute hardest to kill next to it being dormant. The plants intake is slowed way down. So- very hard to kill. Mature plants= hard to kill, same with dormant plants, even from heat stress or cold. Young plants (smaller, less area ) & vigorously growing …. Easier to kill. Why we also want to spray gly on warmer days vs cooler days.
So- I’d say you’re right to some degree. Depends on herbicide. What we do NOT want to do is: mow & “spray the next day”. We want the plant to put on NEW growth (let’s say it’s been regrowing for 3-4 days for example). But for sure actively growing before we spray.
Just to “get in the weeds” a bit if we dug down on effectively timing & killing weeds…. Tender fresh green growth that’s aggressively growing is the time to nuke it.