I don't think that's the case at all-Model Y sales were
up in Q1 2024 in the US (by a small amount).
It was Model 3 that saw a huge decline- and much of that was because they didn't produce hardly
any Model 3s in the first 2 months of Q1 due to Fremont fumbling the retooling/ramp at the factory.
Y gets all the US supply of 2170s except for those going into the Performance Model 3.
There are none left over for the other trims of 3.
The original plan was Y would've been running on structural pack 4680 by now freeing up those 2170s for 3, but that didn't work out.