If the phrase was "1.6x speedup" then I would agree and not have commented. But the phrase is "1.6x faster", which is a bit ambiguous.

That there is disagreement among the commentariat both ways is indicative of ambiguity. (Though, I am assuming no trolling here.)

While not exactly analogous, try replacing it with a percentage and re-evaluate: What does "60% faster" mean and what does "160% faster" mean?