Ehm sorry but no. Sovereignty means you own the stack not that you just choose other suppliers. Build on EU infra means owning a machine room with some servers, having fiber optic good enough for your traffic and that's is.

What the author describe is just a supplier switch still owning next to nothing.

Perhaps the term is overloaded, and a better one would suffice, but the bigger point is to ensure that none of their infrastructure is under the purview of any US entity, public or private.