For WF200, WFM200 or WGM160P, the firmware uses by default the Relative CCA mode which automatically set the CCA level.
This default mode is not recommended to pass the CE RF certification and for this certification the Absolute CCA mode shall be selected.
If you are using the Full-MAC API this could be set with SL_WFX_CCA_THR_MODE_ABSOLUTE using this https://docs.silabs.com/wifi/wf200/rtos/latest/group-g-e-n-e-r-a-l-d-r-i-v-e-r-a-p-i#ga033dca6edbef96e4042d500a10dff9d8
if you are using Lower MAC and Linux driver wfx then you could modify the CCA mode sending a specific frame after the firmware download like this (within a root session only):
# Absolute CCA mode :
echo -en "\x0c\x00\x06\x04\x03\x20\x04\x00\x01\x00\x00\x00" > /sys/kernel/debug/ieee80211/phy*/wfx/send_hif_msg
In order to revert CCA mode in default mode Relative, you could do this below or to reload the firmware:
# Relative CCA mode :
echo -en "\x0c\x00\x06\x04\x03\x20\x04\x00\x00\x00\x00\x00" > /sys/kernel/debug/ieee80211/phy*/wfx/send_hif_msg
Note in the above path, the * in "phy*" could be replaced by an index depending of your target.
This is also indicated in the UG395 in section 8.3 but it could be useful for WF200 or WGM160P.