If your tenth permanent enters the battlefield and then a permanent leaves the battlefield immediately afterwards (most likely due to the "legend rule" or due to being a creature with 0 toughness), you get the city's blessing before it leaves the battlefield
Turning every artifact into a mana source enables explosive turns, and when paired with cards like Paradox Engine, it allows you to cast spells and untap permanents repeatedly, quickly spiraling into overwhelming advantage or outright wins
FromTheShire: Absolute worst case it's redundancy which is never a bad thing to have, but counters decks can easily be doing things on each turn to somewhat break the restriction and this has the upside of counting any permanents, not just creatures
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If you show up with a Grand Arbiter Augustin IV Stax deck, prepare to be the Archenemy
The PT just means the deck shows up (and perhaps gets banned) now, rather than after a season of increasingly Eldrazi dominated GPs