Wow, BL602? That's something new. And as far as I can tell, that's not just a Sonoff S40 clone (S40 is using BL602, as far as I know). That's interesting, I haven't found any BL602-based eWeLink devices yet. I think I only saw a BL602-based RGBCW bulb somewhere, but just once.
Thank you for posting.
Do you remember where have you bought that switch module?