Much like companies declaring they are 100% renewable powered, this does no actually mean only renewable electricity is used 100% of the time. In the last week, 20% of electricity used in Tasmania was from Victoria coal power https://opennem.org.au/energy/tas1/?range=7d&interval=30m/
My council and university also declared themselves '100% renewable powered'. What they do is fund a solar/wind project which will generate the amount of electricity they use over the whole year. Of course in reality their power comes from the grid which was only 26% renewable last year. https://opennem.org.au/energy/nem/?range=1y&interval=1w
Its not a scalable solution! A lot of Australians already have solar panels on their roof which generate more electricity than they use in a 24hour period. But we cannot say we are 100% renewable because we also use power at night, where the electricity is still mostly from coal, especially when theres no wind.
But as more companies try to reach 100% through offsetting the more saturated the grid becomes with renewables, which will make fossil plants uneconomical and force changes around storage. Early adopters pay more for less efficient renewables, late adopters pay more for storage. It's not that terrible. Assuming the books aren't cooked of course.
The article mentions Scotland as an example of a 100% renewable country, when only around 50% of our output is generated this way. There is a great deal of misinformation about this online, partly due to nationalist sentiment and partly due to the government omitting such details from its reports.