Robin2:
??? What A4988 library?An A4988 driver has no limit like that. It requires at least a 1µsec HIGH and 1µsec LOW pulse which implies a max of about 500,000 pulses per second.
...R
It recommends not setting the RPM higher than 200. I would guess it is related to your reasoning about acceleration and skipping steps rather than a limitation of the library itself since setting it to 300 produced the exact same result on my stepper as using the OPs code.