Well, I disagree with pretty much everything in the claims.

First, most real unoptimised code faces many issues before memory bandwidth. During my PhD, the optimisation guys doing spiral.net sat nextdoor and they produced beautiful plots of what limits performance for a bunch of tasks and how each optimisation they do removes an upper bound line until last they get to some bandwidth limitation. Real code will likely have false IPC dependencies, memory latency problems due to pointer chaising or branch mispredictions well before memory bandwidth.

Then the database workload is something I would consider insanely optimized. Most engines are in fierce performance competition. And normally they hit the memory bandwidth in the end. This probably answers why the author is not comparing to EPYC instances that have the memory bandwidth to compete with Graviton.

Then the claims that they choose not to implement SMT or to use DDR5 are both coming from their upstream providers.