There is a mistake in make_rectangle_3points geometry:

It should be

 make_rectangle_3points( 
         make_point(to_real(string_to_array(@lowerleft,',')[0]),to_real(string_to_array(@lowerleft,',')[1])),
         make_point(to_real(string_to_array(@upperright,',')[0]),to_real(string_to_array(@lowerleft,',')[1])),
         make_point(to_real(string_to_array(@upperright,',')[1]),to_real(string_to_array(@upperright,',')[1])

--> Last line !

There is a mistake in make_rectangle_3points geometry:

It should be

 make_rectangle_3points( 
         make_point(to_real(string_to_array(@lowerleft,',')[0]),to_real(string_to_array(@lowerleft,',')[1])),
         make_point(to_real(string_to_array(@upperright,',')[0]),to_real(string_to_array(@lowerleft,',')[1])),
         make_point(to_real(string_to_array(@upperright,',')[1]),to_real(string_to_array(@upperright,',')[1])

--> Last line !

Check your rect geometry with geometry generator in symbology of a seperate layer that you can see the selecting rectangle and adapt it to your needs.