It's false.
https://en.wikipedia.org/wiki/Collision_theory#Steric_factor
The basic principle behind collision theory states that molecules have to collide for a bimolecular or termolecular reaction to occur (termolecular is rare), and their orientations must be aligned well enough for that to occur.
How well the molecules are aligned, in terms of its spatial orientation and location, correlates with how successful the reaction is as it proceeds. Those collisions that are successful cause a chemical change, like perhaps displacing an atom.
For example (hydrobromination):
This is ethene reacting with #HBr#. Let us call the upper-left collision #A#, the upper-right #B#, the lower-left #C#, and the lower-right #D#.
Ethene's molecular orbital depiction:
http://csi.chemie.tu-darmstadt.de/ak/immel/tutorials/orbitals/molecular/ethene.html#orbitals
Collision #B# won't work, potentially because there is not enough room; a lobe on the #2p_x# orbital of the left carbon obstructs the left side of the molecule, and #Br# is large. It's like trying to push a balloon into another balloon.
Collision #C# has two protons hitting head-on... but molecular bonds actively stretch and bend, and ethene's #C-H# bonds stretch in that direction; furthermore, #HBr# doesn't want another proton, so colliding with the bottom-left #H# on ethene doesn't do anything significant.
Collision #D# and #A# are similar, but in #D#, #Br# is approaching ethene. The goal is for #HBr# to get close enough so that ethene can donate its #pi# electrons to acquire #H# and for #Br# to withdraw the #sigma# bonding electrons and disconnect from #H#. #Br# in front with its #p# orbital lobe, moving towards ethene, is too big to facilitate that. It's like trying to push a balloon into a corner---it's hard to make it stay.
So, #A# is the most optimal collision to promote this hydrobromination reaction.
