It is now much quicker, so it is reusing what was installed earlier.
I assume the solution is to just run ]up more frequently. I just don’t use an environment with DifferentialEquations in very often. When installing packages in the future I will just force it to install a version that already exists so I don’t have to wait.
I was just surprised it took so long to update the package. If I added a third package, I am waiting up to 30+ minutes before I can do anything in my new environment. Perhaps that’s just how it is.