Recently I had a conversation with a Chevrolet concessionary technician, it told me that this acceleration is a strategy that some new models with manual transmission have to avoid 'kicks' in the clutch and conserve its useful life for a longer time, simulating the double clutch technique that is carried out in competition, clarifying that the time that the clutch pedal is chosen is not superior to 2 or 3 sec.
It makes sense, since it accelerates the engine when it is unchanged from the transmission so that when engaging the engine speeds and transmission again are similar.
If you have more doubts, in the Chevrolet consent they give management classes for new vehicles. If your client still has the guarantee, you can request it.
I hope it serves something!
All the best!