A write to NOR flash doesn't work in the same way as a read: First, WE bit must be set by a separate command (and it is cleared automatically after completion of programming of a page). Second, writes are page based, i.e. the uppermost address bits must not change during a page programming operation. Third, loading the page's data is completed and programming started by releasing NCS, so this must happen at a well-defined point. Forth, after starting a page write, the flash's busy bit must be polled by read status register operations to find out when the programming has actually finished.
So theoretically, it might be possible to use memory mapped write for NOR flash, however, it would be quite complicated, the OCTOSPI would have to be reconfigured several times from memory-mapped to indirect read/write and vice versa for each page. Not really feasible ...
For SPI-RAM or FRAM it's different, though.
