GHC reports a major collection even when nursery size is far larger than bytes allocated.

andi@horzube:~/prof_comparison$ ~/ghc_head/_build/stage1/bin/ghc ~/ghc_head/nofib/spectral/simple/Main.hs -fforce-recomp -c +RTS -s -A5G -I0 -RTS -prof
   1,343,064,288 bytes allocated in the heap
             456 bytes copied during GC
       4,874,480 bytes maximum residency (1 sample(s))
         298,768 bytes maximum slop
            5214 MiB total memory in use (0 MB lost due to fragmentation)

                                     Tot time (elapsed)  Avg pause  Max pause
  Gen  0         0 colls,     0 par    0.000s   0.000s     0.0000s    0.0000s
  Gen  1         1 colls,     0 par    0.007s   0.007s     0.0074s    0.0074s

  TASKS: 4 (1 bound, 3 peak workers (3 total), using -N1)

  SPARKS: 0 (0 converted, 0 overflowed, 0 dud, 0 GC'd, 0 fizzled)

  INIT    time    0.036s  (  0.036s elapsed)
  MUT     time    0.918s  (  1.064s elapsed)
  GC      time    0.007s  (  0.007s elapsed)
  EXIT    time    0.001s  (  0.002s elapsed)
  Total   time    0.963s  (  1.110s elapsed)

  Alloc rate    1,462,397,314 bytes per MUT second

  Productivity  95.4% of total user, 95.9% of total elapsed

Do we run the GC during shutdown in order to run finalizers? Just seemed odd and I'm not sure why it is happening.