I've had similar issues in the US. The TSA drones tried to tell me that they couldn't tell the size of the bottles just by looking at them (despite the fact that they were smaller than labeled ones that were 3oz). The *supervisor* told me that, "There's no label. There could be acid in there!" ...as if labeled bottles always carry exactly what the label says. Of course, they neglected to respond to my letter/complaint. I should also mention that these bottles had been through the same checkpoint many, many times before.

We used the empty unlabeled store-bought bottles for my wife's hair care products that only came in larger sizes. Now we simply refill other bottles. Nowhere in the US rules does it say anything has to be labeled.