There would be no way for Israel to 'know' that all tunnels were destroyed, or to know a percentage of tunnels destroyed. This is a 'known unknown'.
As Donald Rumsfeld famously said:
Reports that say there's -- that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things that we know that we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns, the ones we don't know we don't know.