Mel's Mix is suggested for bottomless raised beds, like those used for square foot gardening. This is a much different growing situation than container gardening, which is a completely enclosed (except for drainage holes) environment. It does not provide the durability and aeration that the 5:1:1 mix does and that growing in containers requires.

Personally, I don't think the Mel's Mix is even a very good soil for a raised bed but that's a whole different discussion :-))

Thank you gardengal! Wish the 5:1:1 mix was easier to make. I'm not sure I have the time to find all the materials = (