I think this narrative is just meant to distract people from questioning the necessity of the landlord class, they want people angry at a faceless corporate boogieman instead of local landlords (for obvious reasons)
What else do you expect "collective bargaining" to do in a market where every tenant has a different landlord? Your landlord isn't going to care if the tenants of 10,000 other landlords threaten to move out. They only care if you threaten to move out, and then to credibly do that what you need is to show them the unit you could move into which is asking for less.
The real problem is that you need the unit you can threaten to move into to first exist, rather than its construction being inhibited by zoning etc.
Of course, if there are improvements in the rental, you can go beyond the index as the property been "improved", but it's really handy to know each year that it's limited and the exact amount. For 2026 it's locked to 2.14% for example, for everyone.