It’s not about what the API provider can physically support, it’s just about being a polite client. They probably can support 6 concurrent requests without it causing a problem. The point is that if they use offset or page number pagination with a maximum limit of 100, that’s probably a clue that you shouldn’t preemptively grab the first 100 pages in parallel.
Right, that’s my point. Don’t be overzealous obviously. But some concurrency should be expected (and in my opinion designed for and encouraged). There’s a huge gulf between grabbing 100 pages and grabbing the number of resources a browser grabs by default.
It’s not hard to imagine scenarios where an API provider might reasonably prefer n concurrent requests of m batch size over a single request of n * m batch size.
I can more than imagine it, I design for it. Concurrent all the things. The vast majority of GET workloads are either embarrassingly parallel or so badly designed that they fall over with even the gentlest touch (which I’m sad to say I’ve encountered; services falling over from sequential requests!).
Edit to add: this isn’t some wild idea, recent network and web standards have made increasing concurrency both automatic (HTTP/2 and beyond) and tunable (various prefetch APIs).