Since overseas operations might have better conditions, doesn't Taiwan need its own data centers?

You can't draw that conclusion directly. The article questions the rationale of promoting commercial-scale data centers based on manufacturing convenience; it doesn't deny all local infrastructure needs. The author specifically separates digital sovereignty, national defense security, and critical infrastructure for separate discussion, because these involve risk tolerance and strategic autonomy. You should clarify the purpose of building before deciding; commercial operations can be evaluated by cost-effectiveness, but national security needs can't use the same cost logic alone.