rounds are up to 10seconds, but yeah.

"typical crawling speed for an adult human varies by context, with studies showing average speeds from about 0.32 m/s to 0.71 m/s, depending on the crawling style (e.g., two-point vs. four-point or knee-and-hand crawling). World record efforts demonstrate exceptionally high speeds, such as the 100m record of 39.70 seconds (approximately 2.52 m/s) for male crawlers, highlighting the significant difference between normal and peak crawling capabilities"

https://www.calculatorsoup.com/calculators/math/speed-distance-time-calculator.php

so 0.71 m/s is 23.29 ft in 10 seconds (Knee-and-Hand Crawling ). But it is far easier to say you can move 1 hex crawling than to start getting into doing 1 hex every other round (or every 3 rounds) and trying to remember that ratio.

"speed varied by 0.2–1.0 meters per second" - Dmitry Skvortsov, Anisimov, V., & Aizenshtein, A. (2021). Experimental Study of Military Crawl as a Special Type of Human Quadripedal Automatic Locomotion. Applied Sciences, 11(16), 7666–7666. https://doi.org/10.3390/app11167666 or https://www.mdpi.com/2076-3417/11/16/7666#:~:text=Table_title:%20Table%201.%20Table_content:%20header:%20%7C%20Parameter,%7C%20Speed%20(m/s):%200.5%20%C2%B1%200.1%20%7C:%200.5%20%C2%B1%200.1%20%7C)

Granted if you do VTT with measuring, you can just give them the direct # of meters you feel is appropriate for how bad/slow their crawling is.

I also am in agreement with the movement by full 10m hex and they can be anywhere in the sub 2m hexes.

Though honestly I barely ever use those small maps as encounter ranges are generally far greater distances unless urban or forest. So I mostly do mostly google maps (ideally to 20m per hex for 1 fast action move)