There is the problem of a property with joint name.

Since the other 2/3 owner refuse to apportion the rental income, the only solution is through legal process to claim back.
But the cost of legal process may outweight the 1/3 rental income.

A better solution is to propose the other 2/3 owner to buy over the 1/3 share.

As the property technically cannot be sold or rent (sign new tenant agreement), without all party agree.
So propose to the other 2/3 portion owner, stated there may be future problematic/deadlock situation, if not buying over the 1/3 share, as if 1/3 share owner doesn't want to sign, nothing can be done on the property, which virtually all party get nothing from the property.

By right, rental should go to the rental owner accordingly, it doesn't matter the Will stated whether the rental has be to apportioned or not, because rental of property goes to property owner.

But I can see where the advisor come from to give such advise, as
1. legal cost may outweight the income.
2. Making a damage on the relation with the other 2/3 owner, which won't help to solve the situation.