Erstwhile, back in 1928, a then-new species of frog called Microhyla borneensis was described using a type specimen (first specimen, the one which is bound to the newly-described species) also from Gunung Serapi. The tadpoles were thought to live in ponds like normal tadpoles, and the known range of this frog grew over time to include parts of the Malay Peninsula as well as parts of Borneo.

In 2011 another herpetologist doing research on Microhyla frogs in Sarawak realized that the currently understood definition of M. borneensis included frogs of more than one species. In fact, the type specimen itself was the same species as the one described in 2010 as M. nepenthicola, though all of the so-called Microhyla borneensis from the Malay Peninsula and other parts of Borneo were a different, non-pitcher-plant-involved species. So confusing! According to the official international species-naming rules, this meant that Microhyla nepenthicola was an invalid name (or "junior synonym" if you prefer), and now we have to call these Nepenthes-breeding frogs by the considerably less precise name Microhyla borneensis. Meanwhile, the rest of the frogs formerly known as Microhyla borneensis got reclassified as Microhyla malang. Are you following all this?

Then in 2020 some other herpetologists did a bunch of molecular analysis and decided that M. nepenthicola and M. borneensis really were two separate species with slightly different morphology and significantly different lifestyles. So these are back to being M. nepenthicola, for now at least.