I can see a logic in that but what he should do is have a legal agreement so that it is fifty/ fifty but his concerns are addressed in the agreement. That is that he is given a written declaration from the other shareholder as to gold recovered and then he covers himself in the declaration by declaring his and then the other parties separately eg Gold recovered for period xx/xx/xxxx to xx/xx/xxxx - Joe Bloggs 125 grams - Freddy McGripper 97.5 grams. Have a standard covering notification that the other party operates independently and give their contact details and include a copy of their return declaration to you as claim filer.
A clause should also be written in that the other parties costs will be submitted by such and such a date otherwise the contract becomes nul and void after a default period of say 90 days has lapsed.
We never had these things. Everyone, and I have been involved in claims with quite a few others just fell into place due to good honest and honourable friendships and mutual loyalties and also family membership in cases.
A 49/51 percent shareholding will in affect make no difference
Hope that makes some sense.