Yes, giving info about future chapters is a spoiler, it's totally different from giving a trigger warning at the top of the chapter or adding a manhwa tag and both are a must. But here adding the spoiler tag the rape warning would still be there but you would've still seen it and I wouldn't have.
And what? How is the plot not being spoiled?
Well if you head to the comments before even reading the manga then you're basically asking for unwanted spoilers. It's not something I wrote after reading the raws or future chapters which are not already uploaded here. The comment sections are to discuss the current chapters and that's what I did.
Another omegaverse with rape rape and rape. I wonder when the authors will get it in their heads that it's so fucking overused in omegaverse