I'm not sure what you're referring to in “excluded from the clause”. The main clause in the provision provides that if you receive an amount for a restrictive covenant, that will be taxable as income.
The provision does have exceptions for when the covenant is given in the context of the sale of a business, including assets or shares. When there's a sale of a business or shares of a company, the provisions provide that the value of the covenant can be included in the proceeds received for the shares. That would result if the provisions complied with capital gain treatment.
The general thrust of the measure is that if you were to provide a restrictive covenant in the context of a sale of a business, the receipts or the value that relates to the covenant would receive capital gain treatment to the extent that it relates to share sale or asset sale. However, if there were no asset sale or no share sale, the value of the receipts would generally be included in the income as taxable income.