First of all, the accuracy of 1RM calculators is never going to be exact. A 1RM is inherently unpredictable. To my knowledge they are not rigorously tested against different pseudo-rest periods between reps in a set.
I sometimes take several breaths between reps of a squat. The bar is still on my shoulders, though, so it's still a set. In a high-rep context (for which 1RM calculators already become inaccurate) like towards the end of a heavy 20-rep squat workout, I might take five or six fast breaths. In a deadlift, it's normal to take a breath or two and reset one's grip between reps and still call it a set.
An average of 9 seconds between reps for a 10-rep set is pretty far into territory that I would consider not a set in the normal sense. But the distinction is extremely vague, especially for exercises where you're still holding the bar. For a deadlift, where those pauses between reps are complete rest, I'd say they firmly don't count as a set and are more like a cluster of singles.