Race suspension set up
The straps were - as told - only to ensure, that the springs were not getting loose. A more simple sollution than making the shock absorbers shorter.
Generally if you are making the springs stiffer roll bars will be of less importance. The same thickness of roll bar will contribute less to defy the roll. But since the stiffer springs in itself will bring less roll you don't need the roll bar.
Most race cars still have roll bars but they are mainly to fine tune the balance of the car.
I used to have a roll bar like Greek on my trackday car (which still has "road-suspension", Eibach springs and yellow Koni). But I always had minor problems that the roll bar or the brackets fouled the exhaust, the rims or the tyres. They had to be placed very exactly and then it gave a new problem, when I occasionally changed from 15" to 13".
Also I was a little worried that I introduced a bending moment on the reaction arms which are very thin in the metal (they are tubes) and only designed to carry a straight pull.
With the rear anti roll bar the turn in was better (rear wheels taking more of the load). This is more needed on small tracks with limited speed, where the car has a more pronounced tendency to understeer. When driving on fast tracks you have less understeer and often you want more stability. So in fact you could want an adjustable rear roll bar.
I ended up with another compromise (and I use the car a lot on the Nürburgring, where you want a stable car - going off the road could be bad). I fitted longer "spring-bumpstops" from a VW Passat. Don't ask for the number, I do not remember, but they are about 12 cm long an hollow, and they were cut down to 10,5 cm meaning that they do not act during straight driving (about 1 cm gab with empty car). During cornering they make the loaded side more stiff acting halfway as a roll bar.
Two other advantages: They are 62 gram each and the roll bar was 6 kg. And they act as helper springs when you load the car heavy (e.g. extra tyres and tools going to the racetrack) preventing it from lowering much at the rear.
Hoping this helps a little to understand the thing about the roll bar.