The Hang Tite will not prevent runoff and it will not make it thick like syrup.
What it does is helps it "cling" better than using most other soaps out there. Since trying the Hang Tite, my roof cleaning time has dramatically shortened, I use less mix and there is less runoff. I will explain.
By using the Hang Tite from PWP or PWS (both are correct, they sell products and service equipment for decades and decades) it does not fight with your roof chemical (lots of soaps out there will fight with the SH and start to make it weaker) so you get the strength up there that you need.
By having a better dwell time, it is sticking there to do what you want it to do (spraying until it is running off is not only wasteful but looking to harm plants and grass) so the overall time on the job is less since there is less shooting areas several times or more because the roof mix just runs off without being there long enough to do what it has to do. Remember, this is not like house washing, you are not trying to flood the roof, just apply enough chemicals to do the job where house washing you end up flooding the sides by applying the soap but it still ends up doing a good job but roof washing, if you flood the roof you are just wasting chemicals, time and money along with taking a big chance of damaging the greenery.
There are tricks to spraying roofs so there is no runoff but you also have to get enough up there to do the job, just comes in time with practice.
Make sure that you are getting a strong enough % hitting the roof otherwise you are just wasting time and money.
I am adding 1 quart per 50 gallon mix, for steeper roofs I am adding another 1/2 quart. For tile roofs I am using 2 quarts and that does great.
Nobody said it will prevent runoff, but with good application, it will be a lot less runoff than other soaps out there. Most of the dish soaps out there that guys use end up fighting the SH thus making it weaker and using more chemicals for the job and the job takes longer than it should.
By using the Hang Tite, it helps the roof chemical stick up there, it does it's job, you use less chemical and you are done with the job overall a lot faster than using other soaps out there.
A lot of jobs I cut my time in 1/2, most others I easily cut the time by 1/3 there on the job.
By having so much runoff like you mention, you are obviously overspraying quite a bit.
Are you adding other things to the mix besides the Hang Tite and SH? If so, that is probably the problem, I only use those besides water and a few secret ingredients but those are not things that will make or break the runoff issues you are having, you are probably just spraying too much.