The docu page for the nRF9151
https://docs.nordicsemi.com/bundle/ps_nrf9151/page/ip/radio_lte/doc/frontpage.html
contains a link to
docs.nordicsemi.com/.../intro_nrf9160.html
instead of the AT commands for the nRF91x1.
(Same applies for the docu of the nRF9161.)
The right one should be
https://docs.nordicsemi.com/bundle/ref_at_commands_nrf91x1/page/REF/at_commands/intro_nrf91x1.html
and
docs-be.nordicsemi.com/.../nrf91x1_cellular_at_commands_v1.2.pdf