I think what he was probably trying to say is that flu shots are prepared for the strain(s) that are anticipated to be active during flu season.
Since this is simply an educated case, it's sometimes wrong and the strain you're inoculated against is not the strain that people become infected with.
After all the goofy and just plain wrong things he's said about the Covid-19 outbreak and SARS-CoV-2 in the last month, you would think he would be embarrassed and perhaps stick to topics he understands.