I don’t know Radix, so perhaps they use a different merge algorithm than the standard one. The article indicates, though, that nondeterminism was a bug that the company fixed. It does sound like it relies on validators, so perhaps they don’t have open membership, thus don’t allow updates from arbitrary nodes without going through those validators?
Either way, the standard blockchain algorithm doesn’t behave like that.
To be fair, I don’t have a stake in this beyond wanting unambiguous definitions.
This discrepancy was pretty well documented in the Jepsen analysis of the Radix DLT -- https://jepsen.io/analyses/radix-dlt-1.0-beta.35.1
tl;dr: blockchains are not deterministic in the distsys sense