The European laws are not some random thing we made up because we are lazy. It is to ensure workers are well rested and ready for a new working year. Hence in long term it will also benefit employers.
Some personal anecdata: I notice an immediate difference when I come back after a long vacation. The first 2-3 months I work at top efficiency, get probably done twice as much as I would do any other month.
If that was true Europe would have the highest productivity of the world, but it doesn't.
Depends on how you measure productivity. Per hours worked, the top 10 most productive countries is almost only European. Per capita the results are different.