question about CHECK_VALUE for PCGI_UT->LU->exists

Please help clarify the following comment from line# 1768 to 1779 of 
ifo_read.c,
ifoRead_PGCI_UT(ifo_handle_t *ifofile):

  for(i = 0; i < pgci_ut->nr_of_lus; i++) {
    // Maybe this is only defined for v1.1 and later titles?
    /* If the bits in 'lu[i].exists' are enumerated abcd efgh then:
            VTS_x_yy.IFO        VIDEO_TS.IFO
       a == 0x83 "Root"         0x82 "Title"
       b == 0x84 "Subpicture"
       c == 0x85 "Audio"
       d == 0x86 "Angle"
       e == 0x87 "PTT"
    */
    CHECK_VALUE((pgci_ut->lu[i].exists & 0x07) == 0);
  }

Per http://dvd.sourceforge.net/dvdinfo/ifo_vmg.html#pgciut, the 
pcgi_ut->lu[i].exists
stands for "Menu existence flag", which is 0x80 for titles. It make 
sence for the
CHECK_VALUE statement.

However, if the comment above is *true*, the CHECK_VALUE will always 
generate
error messages. Am I right?

I don't have a copy of DVD-VIDEO spec on my hand. So, I can't confirm this.
Would anybody please clarify this question?     Thanks in advance!!

Or, if any person would like to give me a copy of DVD-VIDEO spec, I'd be 
even appreciate :-)

-Ethan