It was more like a polarity that flipped on your upkeep: everything that was phased out last turn phased in, and everything that had been phased in, phased out
Ideally, for each sideboard card you introduce to a deck, you take another from the main deck to keep your deck at 60 cards and thus keep it efficient
It's one of the most exciting new mechanics in Bloomburrow and Zinnia will be the most likely face of that mechanic at Commander tables, making this high rarity version of it highly desirable as an investment
Theres also the Old School (93-94 Magic) format, which allows only sets that were released from 1993 to 1994
Its M19 debut run was aided by the presence of Lichs Mastery
Like other ink errors, theres the possibility for this selective varnish to not be correctly registered when applied