The Matthews are not a landed gentry family and the estate in Scotland owned by David Matthews is not a landed estate as it is understood in Britain, (that is an estate purchased by an ancestor or granted to him by a King in days gone by, and subject to the laws of promigenture in which an estate is handed down for generation after generation from father to eldest son, or nephew or other nearest male heir.)
This piece of land was bought by David Matthews some years ago as a purely commercial venture, in order to develop a luxury hotel complex on it. The Matthews family don't live there. They live in Switzerland and in London. With this piece of land came a lairdship (a purchase.)
Yes, James Matthews may well manage this hotel and the land around it for his father, who is by now probably semi-retired. However, that does not mean that when David Matthews dies his eldest son James will (as happens with landed families) gain the family lands, estates and properties. He may do, he may not.
Spencer Matthews, James's brother stated in an interview that his father does not intend to leave huge amounts of wealth to his children. He believes apparently, in offspring making their own way in life. Therefore, when David passes he may choose to state in his will that all his different business enterprises such as Eden Roc and the complex in Scotland be sold off and the proceeds left to a charitable foundation or to his widow or to another relative altogether.
That property in Scotland isn't entailed (as far as we know) and David is under no obligation whatsoever to leave it to James. He may choose to leave it to him as a business venture, he may not. He himself doesn't use the lairdship title and James himself may or may not use it even if the Highland hotel is left to him to administer.
It's in the lap of the gods, or rather the choice of David Matthews, as to whether his son will be owner of the estate in the Highlands or not in another ten or twenty years. If he isn't then the lairdship will go to the new owner.