That will compress everything sure, but it wont make fluffy buds tight or hard--growing technique and genetics influence those characteristics. Also, I would not recommend using vac sealed bags to cure your meds. Vac seal is good for storage, not curing unless your bags are easy to burp and reseal.
I agree that the genetics have a lot to do with it as well. I have heard of bud hardeners, but I don't use them, or know what's in them. I have heard from other growers here in California that grow, and sell to local dispensaries. That they will vacuum seal for 48-72 hours on about the third day of drying their harvest. I would imagine this could promote mold though. I would think that could bebad for business in the medical marijuana industry. They claim it's part of their process though. They say it's how the buds get their dense for fluffy buds. I tried it one time and my buds were way more dense looking, but I only sealed it for about 24 hours. Than broke it up and cured it in mason jars. They looked like buds you would get in a dispensaries in my local area. I even bought some bud at a local dispensary for comparison. I have also heard of other growers vacuuming sealing in mason jars. I only grow for person use though, and don't know if I would go through the trouble of doing it again for myself, because of the mold factor. I can get pretty good genetics when it comes to plants and if I harvest at the right time they seem pretty dense.