I imagine your way will work just as well as cooking first for a long time, to get everything from bones.
I also imagine the liquid will still leach out the bones further as they set a few months on the shelf. But... when you open and use, you have to strain them, add veggies and seasonings and cook some more, to get where you want the stock to taste.
My old way, is to do all that first,... then can.
Then, when you open a jar, it's already seasoned to taste and has the veggie nutrients in it. My old way is great if you know you want a distinct chicken soup type flavor. (which I usually do)
Your way, leaves you more options for use, as it is very clear, and without Sage and Tumeric and veggies flavors. I think I will can a few using your method. There are times you don't want that strong chicken flavor.
I've learned something new! That's why I love these forums.
Just to be clear, the batch pictured was only flavored with onion because it was intended for a very specific purpose.
Usual batches have more added aromatics and seasonings.
The initial stock was made in a pressure cooker with water just covering the bones so the final stock definitely has strong chicken flavor....the intensity of the flavor can be adjusted as preferred.
FWIW, Ball/Kerr usually addresses issues with a dollars-off coupon.