I don't think I'd trust that guy. I've always read to only use rubbing alcohol or glass cleaner on the blades. This seems to back that up:
"Can you use WD40 to clean wiper blades?
The short answer is yes; you can use WD40 to clean wiper blades. WD40 can act as a powerful solvent, dissolving dirt and debris that has accumulated on the wiper blade. It can also help to lubricate the blade, which can improve its performance and prevent it from skipping or streaking across the windshield. However, there are some important considerations to keep in mind when using WD40 on wiper blades.
One of the most significant concerns with using WD40 on wiper blades is that it can remove the graphite and/or teflon layer from the blade. This layer is essential to the blade’s performance, keeping it gliding over the glass and silent in operation. If this layer is removed, the blade can become noisy or less effective at clearing the windshield.
Additionally, using WD40 on wiper blades can cause the rubber to deteriorate over time. WD40 can dry out the rubber, causing it to crack or split, which can affect the blade’s performance and cause it to wear out more quickly.
So, while WD40 can act as a strong effective cleaner to clean wiper blades, it is essential to use it carefully and sparingly, to avoid causing damage to the blade."
https://www.uniwiper.com.au/can-you-use-wd40-to-clean-wiper-blades/