It can if you select the smallest channel bandwidth and reboot the radio.
On the AP side, the boot up sequence helps set up the communications between AP and all the SMs in the sector. This is one of the reasons a reboot is required when changing channel size. If we allow this option (as currently architected) it would reboot the whole sector to set up the lower channel bandwidth, perform the SA, then reboot again to get back to the desired channel bandwidth. It would creat a lot of downtime.
I see what your saying. I just think we could get a more accurate view of spectrum use with the smaller channel size scan. I am not sure how well the reboot would work. I typically use a script and SNMP to simultanously run the SA on multiple AP's at same time so if one rebooted faster or slower they would no longer run in unison. It would also create a lot more down time in runing a SA.