Prop 13 just limits how much property taxes can increase every year.
This proposed proposition would fundamentally alter how all state and local taxes are voted on. For state taxes a 2/3 majority in the assembly and senate are already required but this bill would also require voters explicitly approve every bill. For local, it would change the threshold for tax increases from ballot measures from a simple majority to 2/3 majority. Both of these changes would utterly handcuff state and local governments.