I can definitely argue that any latency comparison between REST API and Worker Binding is 99% of the

I can definitely argue that any latency comparison between REST API and Worker Binding is 99% of the time not the same root cause. If you have concrete numbers from your Worker's end to end latency, feel free to post later and I can take a look.
Just mentioning it even if you already know, but each D1 query includes the time it took for the SQL itself to be executed (usually at the single digit millisecond level or less), and then you can measure the end-to-end D1 latency within your worker. Example of measuring that in https://github.com/lambrospetrou/d1-starter-sessions-api/blob/6bbd1e5ee971240bb05b669488818f5976d7f81d/src/index.ts#L87
GitHub
Starter repository using Cloudflare Workers with D1 database and the new Sessions API for read replication. - lambrospetrou/d1-starter-sessions-api
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