A 'Multi-Point Inspection' is just that........it does not imply that a rattle will be diagnosed.
You are hearing a rattle or something vibrating while accelerating......that is what the car should be dropped off for......ideally, you should be able to reproduce it while taking a mechanic for a road test......a recording of a noise will not help beyond proving it makes a noise.
It does not take into account throttle position, what area of the car does the sound come from, etcetera.
If the mechanic has to try to reproduce a rattle during a road test, he/she likely drives differently than you and if the sound cannot be reproduced within a five minute road test the car will have no further diagnosis.
Bottom line.....dropping off for a rattle at times, without the car operator reproducing the sound for the tech. is time wasted by both parties.
Rob