Will it help it I told you that 0.75 seconds is only the approximate value and for the super duper hardcore math people there are more exact values such as:
(from game data)
Mallet-0.65s use delay
Pipe Wrench-0.667 use delay
Spanner-0.7s use delay
So it will make the actual time:
Pipe Wrench - 11.34s
Spanner - 9.8s
(this makes more sense now that your recorded values are larger rather than smaller than the expected result, which game processing, latency and possible human error could have caused. Assuming that the spam clicking was more reliable than holding you have about a 0.72s average time longer than the expected value.)
I don't feel like it is worth mentioning most of the time the exact values, because it makes such a tiny difference and only on some very select occasions will it make a difference of more than a second if even. Also, most of the time you will somewhere screw up and add some extra time you could have saved between swings because you weren't fast enough - so those small differences from 0.75 usually get neglected. Not to mention varying latency that adds a bit too.
Ultimately it confuses people more than it benefits them in most cases.
Though I still use the exact values in my programs when I run them because I cannot live with 0.5 seconds of inaccuracy