It encodes this number generated into a seed phrase. whether it is done via JS or bitcoin Core, the resulting seed phrase has an equal chance to be guessed by someone trying every combination of words.
The entropy doesn't change the chance of guessing one seed phrase compare to another.

Are there 24 words combination from words listed in BIP 39 protocol easier to guess than other? If you pick at random those 24 words, you have the same probability to get each of those combination.   

As there are 2048 words, total number of combination is 2048x2047x2046x...x2025x2024. So when you pick one combination, you have one chance out of 2048x2047x2046x...x2025x2024 to get one specific combination independently from how it was generated