Compiling cuFFT Fortran program with .f90 suffix fails, but .cuf suffix links correctly

Question

I have the following example fortran code cufft_example.f90:

      program cufft_example
      use cudafor
      use cufft
      use iso_c_binding
      implicit none
    
      ! Parameters
      integer, parameter :: nx = 8
      integer, parameter :: batch_size = 1
      integer, parameter :: array_size = nx*batch_size
    
      ! Complex data arrays
      complex(8), dimension(array_size) :: data_in, data_out
    
      ! cuFFT plan handle
      type(c_ptr):: plan
    
      ! CUDA error variable
      integer :: cuda_err
    
      ! Initialize data
      data_in = 0.0d0
      !data_in = [(dble(i), 0.0d0) :: i = 1, nx*batch_size]
    
      ! Initialize cuFFT
      cuda_err = cufftCreate(plan)
      if (cuda_err /= 0) then
        write(*,*) 'Error creating cuFFT plan'
        stop
      end if
    
      ! Set cuFFT plan parameters
      cuda_err = cufftSetAutoAllocation(plan, 1)
      if (cuda_err /= 0) then
        write(*,*) 'Error setting cuFFT plan parameters'
        stop
      end if
    
      cuda_err = cufftPlan1d(plan, nx, CUFFT_Z2Z, batch_size)
      if (cuda_err /= 0) then
        write(*,*) 'Error setting cuFFT plan parameters'
        stop
      end if
    
      ! Execute cuFFT forward transform
      cuda_err = cufftExecZ2Z(plan, data_in, data_out, CUFFT_FORWARD)
      if (cuda_err /= 0) then
        write(*,*) 'Error executing cuFFT transform'
        stop
      end if
    
      ! Clean up cuFFT plan
      cuda_err = cufftDestroy(plan)
      if (cuda_err /= 0) then
        write(*,*) 'Error destroying cuFFT plan'
        stop
      end if
    
      ! Print results
      write(*,*) 'Original Data:'
      write(*,*) data_in
      write(*,*)
      write(*,*) 'Transformed Data:'
      write(*,*) data_out
    
    end program cufft_example

I have tried compiling it with:

nvfortran -fast -cudalib=cufft -o cufft_example cufft_example.f90

but i get the following errors:

NVFORTRAN-S-0155-Could not resolve generic procedure cufftcreate (../cufft_example2.f90: 26)
NVFORTRAN-S-0155-Could not resolve generic procedure cufftsetautoallocation (../cufft_example2.f90: 33)
NVFORTRAN-S-0155-Could not resolve generic procedure cufftplan1d (../cufft_example2.f90: 39)
NVFORTRAN-S-0155-Could not resolve generic procedure cufftexecz2z (../cufft_example2.f90: 46)
NVFORTRAN-S-0155-Could not resolve generic procedure cufftdestroy (../cufft_example2.f90: 53)

suggesting that the cufft libs are not being linked properly.

Though the example that comes with nvhpc toolkit nvhpc/23.3/Linux_x86_64/23.3/examples/CUDA-Libraries/cuFFT/test_fft_cuf/tfft1.cuf:

    program cufft2dTest
      use cufft
      implicit none
      integer, parameter :: n=450
      complex :: a(n,n),b(n,n)
      complex, device :: a_d(n,n), b_d(n,n)
      real :: ar(n,n),br(n,n),x
      real, device :: ar_d(n,n), br_d(n,n)
      integer :: plan, ierr
      logical passing
    
      a = 1; a_d = a
      ar = 1; ar_d = ar
    
      ierr = cufftPlan2D(plan,n,n,CUFFT_C2C)
      ierr = ierr + cufftExecC2C(plan,a_d,b_d,CUFFT_FORWARD)
      b = b_d
      write(*,*) maxval(real(b)),sum(b),450*450
      ierr = ierr + cufftExecC2C(plan,b_d,b_d,CUFFT_INVERSE)
      b = b_d
      x = maxval(abs(a-b/(n*n)))
      write(*,*) 'Max error C2C: ', x
      passing = x .le. 1.0e-5
    
      ierr = ierr + cufftPlan2D(plan,n,n,CUFFT_R2C)
      ierr = ierr + cufftExecR2C(plan,ar_d,b_d)
      ierr = ierr + cufftPlan2D(plan,n,n,CUFFT_C2R)
      ierr = ierr + cufftExecC2R(plan,b_d,br_d)
      br = br_d
      x = maxval(abs(ar-br/(n*n)))
      write(*,*) 'Max error R2C/C2R: ', x
      passing = passing .and. (x .le. 1.0e-5)
    
      ierr = ierr + cufftDestroy(plan)
      print *,ierr
      passing = passing .and. (ierr .eq. 0)
      if (passing) then
        print *,"Test PASSED"
      else
        print *,"Test FAILED"
      endif
    end program cufft2dTest

Compiles and passes the test fine with:

nvfortran -fast -cudalib=cufft -o tfft1.exe tfft1.cuf

Why would the library be linked properly when the suffix is .cuf, but not .f90?