It was specifically about methanol. Methanol wasn't explicitly used as a denaturation agent but ethanol methanol mixture sales were (forced to be) allowed. Can't find much in English but here's a brief story.

Methanol sales were banned in Finland prior to EU and Finland applied for the exemption already in the EU application in the early 1990s. It was finally granted in 2019. Probably around 500 people died and many got blinded meanwhile.

https://yle.fi/a/3-7841018