If my desktop is sleeping, turning off my bathroom light will 2 out of 5 times wake up the pc.
It's a fluorescent lamp, so it is likely that it makes considerable noise on the electrical circuit when being toggled (and it's a small apartment so all lights and outlets are on the same circuit)
I believe I read a forum post from someone else experiencing the same thing, and they also had a Gigabyte motherboard. So it might be related to their bios/firmware implementation of wake-on-lan in some way.
Even though many phone plans today have unlimited texts, some still don't. A delivery report is basically a second SMS, that you then have to pay for, so I think that is why it is an opt-in feature.