I still grow indoors without any buffer to loadshedding.
With the current stage 4/6 schedule, i run my veg on a 24h on cycle. Its not the Interrupted light cycle that causes issues during veg though , but interruptions to the 12h dark cycle during Flowering that is crucial. That 12h or more dark time is critical to the florigen hormone function responsible for stable flowering without stress responses presenting.
When in flowering, i ignore the loadshedding times. See the loadshedding during lights on as a prolonged cloud cover. Its really not the lights that are an issue though. Its that 12h dark part of the cycle and the ventilation at that time. You need to keep the fans going during lights off/loadshedding times to avoid PM. Leaving the tent open at times when the lights would normally be on, will avert the PM. But during lights off/tent closed, airflow is that thing that HAS to still happen or PM will wreck your grow within a week.