so none of the previous more esoteric superconductors were ever measure for zero resistance?
https://sci-hub.ru/https://link.springer.com/article/10.1007...
The difference now is that we're seeing a premature preprint being replicated in real time.
Even in that paper, the authors note: "The way the samples have been prepared seems to be of crucial importance: Michel et al. [21] obtained a single-phase perovskite by mixing the oxides of La and Cu and BaCOa in an appropriate ratio and subsequent annealing at 1,000 ~ in air. We also applied this annealing condition to one of our samples, obtained by the decomposition of the corresponding oxalates, and found no superconductivity." And you can see that in their resistivity/temperature graph of samples prepared using different protocols.
Considering how that preprint has sparked interest in other research institutions and multiplied the resources allocated to the problem, I would say this publication was not premature, it's most other research results that are late.