[kimixa]

The calculations within each unit may be, true, but routing and data transfer is probably the biggest limiting factor on a modern chip. It should be clear that placing 16x units of non-trivial size means that the average will likely be further away from the data source than a single unit, and transmitting data over distances can have greater-than-linear increasing costs (not just resistance/capacitance losses, but to hit timing targets you need faster switching, which means higher voltages etc.)

[dzaima]

Both Intel and AMD to some extent separate the vector ALUs and the register file in 128-bit (or 256-bit?) lanes, across which arithmetic ops won't need to cross at all. Of course loads/stores/shuffles still need to though, making this point somewhat moot.