Thank you - I would never have found that. The RT3200 is the first OpenWrt target I've used that with country code set to US could not set transmit power up to 30 dBm on 2.4 GHz channels 1-11 (RT3200 limited to 28 dBm), U-NII-1 channels 36-48 (RT3200 limited to 23 dBm) and U-NII-3 channels 149-165 (RT3200 limited to 27 dBm).
I've experimented with more OpenWrt targets than I care to admit over the years that could set tx power up to 30 dBm: TP-Link Archer C7, Linksys EA6350v3 and EA8500, Askey RT4230W, Dynalink DL-WRX36. I half suspected the RT3200 amplifiers were just not capable of a full watt. Looks like it is the defaults used for the OpenWrt builds instead.