I have only used Cutless which controls over all growth. I think the one you are talking about controls vertical growth and promote horizontal growth. I think Green Dr alluded to this as well. I have never used it.
Those vines are a PITA and you have to find them and cut then at the ground. If possible pull them but that is not always so easy. Even without a PGR they will cause grief.
I think you can leave some clipping blown back under the shrubs but the lion share should be removed. Clippings can cup water and promote mesquites too.
We can dump them and better yet take them to a mulching facility offered by many land-field operations.
I do get tired to pay for stuff to be mulched and paying to buy the mulch but such is life.
Nothing should go down the storm drains. It is against the federal law. While it maybe common practice, you do not want to be the guy that makes the headlines when the government decides to send a message. Clients also want to seen as greener. If you want to shred and mulch then that is another program.
Some times it takes a few applications for the PGR's to kick in. I hit myown shrubs and they did not grow much for 18 months. They do work but it varies by plant type and app rate. Clip and treat per the lable, often they should happen at the same time or within 10 days.