No this is false... think of moon light. As long as there’s no crazy light stressing your plant out causing it to start photosynthesis it will be fine. Trust me. It’s only when you have light that’s powerful enough to cause photosynthesis. Trust I’ve done SO much research. Now if a grow light were to be left on or reflecting off something bright enough to stress the plant out then I’d worry but I’ve been growing in a 2x3 closet that I Have To leave the door cracked to let fresh air as I have no exhaust. My lights shut off at 6pm and I still chill in my room with the door cracked and even tho a tad of light gets in... it’s darker in there than the moon light would be, causing NO PHOTOSYNTHESIS and buds are forming beautifully NO SIGN of hermes and I’ve seen people that let WAY more light in with no problem. It depends how much light, how long, and where it’s shining. But just a small leak of light that’s not lighting up your plant should be fine