reftex-initialize-temporary-buffers

reftex-initialize-temporary-buffers is a variable defined in `reftex-vars.el'.
Its value is

nil

Documentation:
Non-nil means do initializations even when visiting file temporarily.
When nil, RefTeX may turn off find-file hooks and other stuff to briefly
visit a file.
When t, the full default initializations are done (find-file-hook etc.).
Instead of t or nil, this variable may also be a list of hook functions to
do a minimal initialization.

You can customize this variable.