Presumably for people who haven’t read the manga in Japan yet.
Basically Shueisha is re-releasing:
The earlier School Chapter standalones
The Death-T & Monster World Arcs
during April 8th, 2016
And Duelist Kingdom Part 1 during April 22nd, 2016
Shonen Jump Remix is basically an omnibus version of major titles, sold at convenience stores. However, they’re low paper quality due to being a cost-effective Omnibus, and are intended as a short shelf-life product (i.e. limited run) with low chances of reprints.