I wouldn't even be surprised if the "Chapter about Big Mom" was simply an assumption the Korean leaker is making due to the spoiler title. The title could also just as likely mean its about Queen mostly than Big Mom. Or its both. Like I wouldn't 100% expect Big Mom this chapter, not yet at least, but we can 100% expect an ancient zoan getting their ass kicked at the end.
Just saying. There are have been instances were we've gotten monday spoilers and the leaker makes guesses. Here's an example where he was right:
- Chapter 998 Title "Ancient Species".
- Korean leaker has no complete information yet but he/she says something about Tobiroppo.
- Maybe we discover all of their unknown powers in this chapters.
- At the end of the chapter Yamato appears (we can see her in the picture).
- No Break Next week
He simply guessed it was about the Tobi Roppo revealing their fruits, and you can see its the same 3/4 available bits of info we get if they are monday spoilers:
- A title
- a single line description which sometimes doesn't exist/may be based on their guesses
- a description of the last page (if visible)
- break/no break info
Here's an example where he didn't say anything but the title and break status:
https://worstgen.alwaysdata.net/for...spoiler-summaries-and-images.7982/post-779247