Right, especially since a few paragraphs down, he introduces all the different modes, including ECB.

To me at least, it makes sense to introduce a complex topic gradually, in stages. But regardless, I still agree that the wording in the paragraph you called out could be improved for better clarity.

Sorry to keep hammering on this, but ...

I don't know in what context it would be reasonable even as a simplification to say that block ciphers are semantically insecure like that. Anyone who listed that as a disadvantage to block ciphers should be regarded as confused, not speaking from a big picture perspective.

Furthermore, even if you're going to explain it that way as a result of building up the complexity gradually, you need to explicitly "unring" that bell, e.g. "Earlier I said X, but actually Y...". This author didn't.