That's definitely not accurate.
* https://en.wikipedia.org/wiki/Time_in_Europe
France should probably, AFAICT, be in WET (like the UK) and Spain definitely should be. Solar time offsets are quite off for them:
* http://blog.poormansmath.net/how-much-is-time-wrong-around-t...
* https://github.com/stefano-maggiolo/solar-time-vs-standard-t...
The only real downside I see is that if the day number changes during your "day" it could be confusing. However I think we will quickly learn to deal with it (overnight shifts have been a thing forever and doctors seem to manage). Plus we already have a weaker form of this when we are talking about late-night activities so I think we will figure it out.
Humans have circadian rhythms that have health effects:
* https://en.wikipedia.org/wiki/Chronobiology
See my comment linking to various position papers of the scientists who study in this field:
* https://news.ycombinator.com/item?id=26088541
They generally want to get rid of DST completely and stick with Standard ("winter") Time all year round. (I don't know enough to gainsay them.)