There wouldn't be much point in that, as when they promote a discount the price they compare it to would need to be the LOWEST over the previous 30 days.
Yeah I guess if they were actually following that rule but they definitely aren't. It's not prime day anymore so I can't link an example but I was looking at TVs when it was prime day and specifically noticed one where there was a spike for a couple of days just before prime day and that was the discount they claimed.
Then please report them to your national consumer protection authority. These kinds of violations are subject to a fine of up to 4% of the annual turnover in the violated member state.