What are your experiences Printing PLA and PETG together in a single Print?

I'm pretty new to 3D Printing and just learned that apperantly PLA and PETG don't like sticking together. I have printed with both of them before without much issue tho?

Given that I plan on doing a Massive 4 Colour Print for Christmas, which will use Black & White PETG HF, Red PLA Basic and PLA Metal, I was wondering if this really is as Worrysome as people make it out to be? What are your experiences with mixing Filament Types like this?