It does smack of redundancy, especially in the context you provided, where the statement is further reinforced by the preceding 'was and remains'.
Logically anything that is inconsistent will be consistently so, since 'inconsistent' covers any behaviour apart from actual consistency. It's like saying that something is consistently chaotic. What is 'inconsistent' chaos? It gets pretty metaphysical pretty quickly.
For that reason, I'd say the best use for the phrase (and probably the reason why many articles use it), is to create humour.
On the other hand, it can also be used (and is likely the intended meaning in the example you cited) to mean that the results of the exercise fluctuate widely, but also in a predictable way. In which case I suppose the usage is valid, but still a little redundant. I'm not aware of a single term that could capture the sentiment, though.