The three areas the United Kingdom is willing to concede, apart from the Truce States, are undesirable to Carlo.
In the previous conflict over Borneo, Spain has already occupied the Kutai Sultanate. If Spain were to expand further south, it would take over all lands held by the Netherlands in Borneo.
Consequently, the situation in Borneo transformed from a Spanish-Dutch colonial rivalry with the United Kingdom as an outsider to direct competition between the United Kingdom and Spain.
Carlo does not want colonial competition with the United Kingdom in such distant locations, as the time required for travel between the mainland and Borneo involves considerable expenses.
The same logic applies to New Guinea. Carlo ordered the Philippine Colony to dispatch colonists to New Guinea to delay other European powers' colonization efforts.
Currently, Spain's colonization in New Guinea is quite successful; with British support, acquiring half of New Guinea wouldn't be exaggerated.
