Could have been a useful pice but too many variables not least freehand shooting. Someone needs to do a more “ scientific “ trial using stable rests and vary the distance that the twigs/grass interference is from the target. We all “ feel” that slower heavier rounds deflect less but I have seen little in the way of facts to support that
It might not have been done to full scientific standards with all the variables taken into account so you get the ability lots of statical analyses etc etc.
But basic physics and mathematics will tell you that a projectile weighing 10 grams going along at 750 metres per sec that hits a glancing blow on a stationary twig that weighs 100 grams will result in an equal and opposite reaction that will cause that bullet to veer off course. By how much will really depend on the angles of impact, the construction of the bullet etc etc. etc.
And the physics will change if it is a 50 gram bullet going 600 metres per sec out of a big bore rifle hitting the same twig.
If I could remember my A Level physics you could produce the mathematical answers to all of this - its a question of vectors and forces.
My take on all of this is that it’s probably not worth adding all these variables into the equation unless you absolutely have to. Make the first shot count, and if its not an absolutely clear shot then just wait a while until it is a clear shot, or move until it is a clear shot.
You can have the same argument on the road.
If you are on a motorbike and you hit a traffic cone at speed you are going to come off, in car you will swerve and do quite a bit of damage to the front of the car and might well swerve into oncoming traffic, if you in a big truck you will damage the paintwork.
Make that traffic cone into a six inch diameter tree or lamppost and you hit it at any speed the results are not going to be good.
We can postulate endlessly on best vehicle to be in when you hit a tree.
But the best answer perhaps is not to risk hitting a tree in any vehicle and drive accordingly.