Perhaps chartered?

Perhaps it should be looked at from the contractual perspective. Land-Lease and destroyers for bases were contracts. Transferring destroyers was perhaps not allowed due to the clauses, as J. mentions.

The Dutch had no bases to offer so that bargaining chip was out. They were however in possession of the larger part of the Netherlands Bank gold reserves. Therefore it could well have been a financial transaction in the form of a "bare-boat" charter.

Under such a contract, a ship will be operated and crewed by another party for a defined period of time, but ownership is retained by the original owner. This defeats the "transfer" clause in the land lease, and is perfectly legal.

These contracts were quite common when a Navy needed passenger liners for troopships, so I can't see why it wouldnt apply to warships as well.

Note I have no evidence to support this, but being that there were a lot of dutch shipping line directors and lawyers in London and New York, it seems a logical avenue.