Health professions offices will not be able to provide this information. They may be able to provide raw numbers, but certainly not percentages. There are missing denomimators.
Many, perhaps even most, pre-meds have no contact with the HP office until they request a committee letter of recommendation. Because pre-med is an intention, not any specific major and one that does not require specific support from the school-- not even a HP committee letter if you want to be technical (committee letters are preferred but not required for a med school application), the HP office has no idea exactly how many pre-meds are attending the college. The HP office will not know which students plan to do a post-bacc or even exactly how many plan to apply to med school post graduation.
Students who attend post-baccs generally get their committee LOR–if they choose to use one-- from the post-bacc, not from their undergrad. (This means their data is not available to the undergrad HP office, and often the undergrad HP office is unaware that those individuals even applied med school.)