The question is the standard to which a clause in the general terms of a contract must be judged is given (a) by article 6:233 (which posses that a clause is destructible when it is undue burdensome) or (b) by article 6:248 (which gives a general rule that obligations may not be unfair or unreasonable) both of the Dutch Civil Code. The answer is that parties have a free choice in which article the base their claims on, which is a general rule in Dutch law when more than one option exists.
The rules in chapter 6.5.3 of the Civil Code (partially based on Directive 93/13/EC) are tend to protect the position of the counterparty of the person using the general terms. This goal is not served well if the counterparty is withheld the option to invoke the protection which article 6:248 offers. The difference in the result of the application of both rules gives no reason to judge that this choice should not be offered, since it does not lead to an unacceptable result for the user of the general terms.