It's just legal jargon for the club to cover their arse in future.
They may have to be relocated for any number of reasons. For all we know, there could be 'services' that run under ground in that location, that may have to be dug up at a later date.
They may to choose for one reason or another, to redevelop the surrounding area around Anfield, again, at a later date.
As for the 'destruction' of stones.
Lets say they decided to relocate or remove them at a later date, and said that people could come and claim the stone (for a small fee, I'm sure
) for themselves.
Lets say 99% of peole claimed them, but for one reason or another, many weren't claimed. What are the club to do, store them indefinitely? Of course not.
The club would store them for a limited time, then dispose of them.
Then, lets say, after storing them for a few years, they were disposed of. Then lo and behold, a few years after thet someone came forward to claim a stone, after it had been destroyed!
So the 'destroy or dispose of' element, is just legal jargon to cover their arses at a later date.