Ive noticed the same.
Recently I found an impulse sealed bag with a faulty one way valve.
The beans definitely seemed less matured.
I bought a bag of roasted beans last week that I prefer at 7 days post roast. They had only been roasted the day before so I asked for the bag not to be heat sealed, figuring they should be ready sooner.
I usually roast 500g lots and decide on whether or not to heat seal both 250g bags depending on projected use.