"Spanner for causal transactions" would be more accurate.
P.S. Not sure what you mean by "hidden communication channels."
No, it is not. It does however require communication.
Additionally, what's true in an absolute physical sense, is somewhat removed from what's practical engineered product. For example, we cannot literally make a physical part that is perfectly 1 meter in length. This has not stopped us from making everything from microchips to spacecraft.
> Abel puts in money in Spain, Beth removes it in Australia -- do you charge an overdraft fee/interest? (N.B., Abel and Beth may be names of HFT algorithms.)
Spanner handles this by using two phase commit over sets of independent consensus replication groups. By using TrueTime's ability to provide absolute intervals, it can wait out uncertainty windows to enforce the total order.
> P.S. Not sure what you mean by "hidden communication channels."
Schemes such as lamport and vector clocks require all messages exchanged to include clock data. If two clients establish their own communication channel using some other protocol, they may not agree on the same event order, because the system has no way to know it needs to advance the logical clocks based on this hidden communication.
Spanner in combination with TrueTime avoids this limitation. External observers will see the same commit order in real time, regardless of how they communicate.
Please read and understand the papers to get what you're missing.
This is the whole point of the system, and what the article covers.
What you're saying about time isn't even exactly true in the general case where we need account for relativity. While observers of clocks in different locations may not agree on clocks alone, they will agree on the total spacetime interval.
In any case, accounting for relativity is only necessary in high precision radio frequency systems operating between ground and orbit like GPS. And even then we can still track the frequency and phase offsets of the oscillators in real time and establish their relationship to idealized ephemeris time.
So yes, the sentences in the article DO make sense.
EDIT: at least the ones concerning time and consistent orders due. The words about effectively CA are ... not great.