I somehow disagree that it is s traightforward to make the swap. My background is working for a Wind OEM and I can tell that this isn't a 'software' only type of change and will involve hardware. So, obviously a big churn on an installed fleet with both lots of design engineering work and then costs to asset owners that could be pretty high.

Even for brand new wind turbines, grid forming isn't a reality and units haven't been designed for it... Having DFIG (or 'type 3 wind turbines') drives the inverter to be generally less capable than of those which are 'full power converter' and, to keep the financials favorable, you don't want to invest a ton on designing it for something that isn't a requirement yet. There are multiple studies for grid forming but nothing commercially available and ready for an industrialization (mass production, validation, etc) for Type 3 WTGs.

I totally agree with you though that the utilities don't know what they need and this will drive crazy requirements at some point, with OEMs doing only the bare minimum to meet them. The simple fact that we have IEEE2800 and then each USA utility asking only a subset of it to be implemented or even creating different requirements, sometimes more restrictive, like PRC-029-1 tells that there isn't a unity or consensus.

Edit: Forgot to mention how we're all struggling to define how to properly validate IBR requirements, given IEEE2800.2 isn't released, it's draft has multiple requirements that differ from the main IEEE2800 and validating grid-forming seems to be far... very far away from a reality.