Yes, it is largely true that nationalism was indeed non-existent in the Philippines before the 19th century.
This is mainly because, up until then, the Philippines was a collection of principalities, rather than a sovereign state with a sense of unified national identity.
How nationalism came to the Philippines in the 19th century
By the 1800s, The Philippines had been under Spanish rule for 3 centuries.
What made this time special for Filipino nationalism?
The generation of Spanish-Filipino creoles were become the most numerous and increasingly powerful (holding government positions etc).
This class, which was still looked down upon by the 'peninuslares" or ethnically pure Spaniards, was able to grow in size - and power, based on the following factors:
- economy
- education
- secularization of parishes.