Vilas,
So itīs understood that below 700 AGL and in LOC/GS captured mode, switching off APP will not untune ILS frequency and too late to activate secondary.
Above 700 AGL, FD off, APP off and BIRD on will "erase" ILS APP mode on PFD so that a visual can be flown without any nuisance regarding LOC or GS deviation from initail ILS loaded on MCDU.