I had an interesting chat with a cisco tech last wednesday over this one.
Meraki ( and cisco) couldn't do this before because the hardware wasn't powerfull enough.
The Catalyst 9300 has some new kind of powerfull silicon ( asic) what can do this.
And again it's more dynamic configurable by software.
in Cisco world its called SDA ( Software defined access) so why wouldn't meraki use the same ( very good) hardware for their new layer3 switch?
The stackpower and seperate modules for uplinks in the Catalyst series are just great, something meraki really missed.
On the other side... standarisation in hardware between cisco and meraki coud drop the price ( or make cisco more profit 😉 )