Is NIX_CONF_DIR respected by nix repl?

When I do a

NIX_CONF_DIR=$(realpath .) nix repl
repl> d = ...
repl> :b d

the build command spawned always takes the value of max-jobs as set in my user’s nix.conf not the one set in the nix.conf in pwd.

Is that the regular behaviour and how can I achieve what I wanted ?