Find (?) performance

Hi,

In https://code.kx.com/q/ref/releases/ChangesIn3.5/ they say that search performance is improved.

Why a?b is much slower than a?/:b in this case ? They give the same result.

q)a:-1234567890 123456789,100000?10;b:1000?a;

q)system each(“ts:1000 a?b”;“ts:1000 a?/:b”)

14905 5259424

852   28528  

Thanks,

pahihu