{mode, ...} overrides variables explicitly set in the profile

[brigadier]

Example of the profile:

{profiles, [
    {prod, [{relx, [
                    {mode, prod},
                    {include_erts, "/path/to/erlang/26.2.1/"},
                    {sys_config, "./config/prod.config"}
    ]}]
    },
    {dev, [{relx, [{dev_mode, true},
                   {extended_start_script, true},               
                   {sys_config, "./config/dev.config"}
    ]}]
    }
]
}.

or

...
{include_erts, "/path/to/erlang"}
{mode, prod},
...

Regardless of the order of declaration and of everything else the include_erts is set to true because {mode, ...} always follows the {include_erts, ...} in the Config variable in the rlx_config:to_state/1.

This behaviour contradicts documentation

You can override options that the modes expand to by including explicit setting them. For example, if you wanted to keep the debug info in the BEAM modules you can use a configuration like:

[
  {mode, prod},
  {debug_info, keep}
]