Now that you mention it, I cant remember seeing many reports of people growing truffles in bags. Perhaps jars are a factor also. It still doesn't explain why there was such a difference between the three portions though.
I was limited by the size of my pressure cooker. It is a small family sized one that does 11.6 PSI. I had to keep it at pressure for about 150 min to feel reasonably confident that the substrate was going to be sterile. By using bags, I managed to squish all three inside for a single run. It would have taken forever doing one jar at a time, not to mention the difficulty in finding jars that would fit inside when raised off the base.
Buying a large pressure cooker would lead to lots of questions being asked. It's not easy going about doing dmt extractions and growing truffles right under the nose of an unsympathetic spouse. It is quite entertaining in a 'breaking bad' fantasy sort of way
but very inconvenient.