Considering both the EU and the US are in the Northern hemisphere, there is no ambiguity. Same as it's perfectly fine for public clocks to indicate the time without mentioning the time zone, even though the meaning of a given time is location-dependent.
From the perspective of people who live in the Northern hemisphere, there is no ambiguity; but The Register has readers in the Southern hemisphere, and it is a continual source of irritation for southerners that writers, either through ignorance or sloppiness, fail to realise that 'spring' is ambiguous. The Register has a global readership.
It is indeed perfectly fine for public clocks to omit the time zone, as they are not intended for use by people on the other side of the planet. A very small proportion of clock faces are visible from multiple time zones. An Australian does not look at the face of Great Clock of Westminster on the Elizabeth Tower of the Houses of Parliament to tell the time; and neither does a Parisian. They don't have 'line of sight', and would have to take special measures, such as a video-link, to see it. The Register's text is available to all via the Internet, and it has contributors from both hemispheres, as well as readers.
So your comparison is invalid, and it is sloppiness.
Northern spring has started. The deadline ("A new EU-US transatlantic data flow agreement is expected to be finalized by the spring of 2023") has passed.