The Netherlands instituted rather draconian measures for Schiphol transit passengers in 2020 that have been partially relaxed. It was one of the first countries requiring a negative PCR-RT test even from passengers who were mainly changing planes without entering the country.
KLM has sent me several reminders about checking the transit and entry requirements, as I have flights with them coming on Friday and Monday. The information they have sent by SMS compared to email is confusing.
The information about the Spain entry requirements is correct for travel from Estonia. The second message, although not incorrect, is confusing or misleading.
There is no requirement of having a PCR-RT test administered within 24 hours before departure to the Netherlands for transit passengers. You can transit with a PCR-RT that is not administered more than 72 hours before ARRIVAL.
You obviously need to comply with the requirements of the destination country as well.
This transit information is not clearly identified in the email either. They could have had it as an Option 3, as there must be many passengers transiting in Amsterdam on KLM.
The Netherlands has dropped the negative test requirements for arrivals or transits from Finland (must have been this week), but I am flying out from Tallinn.
Having to do a test in Barcelona merely to transit through Amsterdam on Monday at some point over the weekend is annoying because destination country doesn’t require one.
Netherlands could simplify these entry and transit rules. Some test requirements are based on your departure flight time to Amsterdam while the transit one is based on your scheduled arrival time in Amsterdam.