Every post-war Defence White Paper has been overcome by events and then completely ignored the minute the government of the day shifts it's limited attention and resources. The very infrequent modern ones have been so vague as to be useless or were functionally shelved within a few years.  Back loading most of the spending and spreading it over a decade or two tells us all how this will likely play out.
If they attached a significant directed purchase on a platform or new capability to start, it might have carried more credibility.