I think Sony isn't defensive. I think they just don't give a fuck.
This generation they are dominating the hardware sales, software sales, 1st party quantity and quality of games that are selling better than most of their studios ever did, marketing deals with the main 3rd party multi games, game subscription service, game streaming service and non-mobile VR and so on.
Just making the common sense stuff strategy of continuing with the same plan but adding the proper next gen improvements (and seems it's the case for what we know officialy, and from what is rumored/leaked: same hardware architecture but more powerful, full BC, improved next gen PS Now, super fast SSD, RT, etc.) they will dominate again. Basically now they only need to make sure that the price isn't too expensive I'd say max $499, but $399 if possible and to make sure that in terms of horsepower aren't way below Xbox.
I'd bet they agreed to use pretty much the same hardware to reduce costs faster and to make sure they have similar horsepower, something that also benefits the 3rd party publishers.