I can agree with this, except Umbrel is not actually the Bitcoin node, Bitcoin core (an application that runs in the Umbrel Operating System) is the node. There are actually two nodes that run on Umbrel, a Bitcoin node and a lightning node. The Lightning node needs the Bitcoin node, but the Lightning node in the case of Umbrel is actually LND.

Also....If you buy a 4tb HDD (I happen to have one in my set up) as a secondary drive, you can run both things on the same computer. The reason I agree however, is because its for the best if you use like a PfSense router to logically separate your lightning node (your money) and your other applications running for fun like Nost, but this is for security, not technical limitations.