HP and Oracle have been reaping the benefits of this for at least two decades now. We put databases on Oracle that should be handled by Postgres or MariaDB since DoD prefers Oracle. We would buy useless HP software because we were a HP shop. I fought to get a non HP solid state array for our data, it was an epic battle (in the end I won, on the extreme we had 6 to 7 hour processes cut down to under an hour, the HP equivalent could not replicate that at the time).
So i can see DoD moving to Azure and then get the vendor lock in and in 10 years if they want to move the cost will be so extreme it will either cause taxpayers a ton of money or not be realistic.
As impossible as it sounds, and somewhat impractical, i would rather see a vendor agnostic approach and DoD spread across multiple gov clouds. i guess years has gotten me jaded with government spending (wait, what, how did we buy 2 extra $50k Cisco chassis and then keep them in storage for 3 years....).