It means you pretty much act like MO, but you don’t hold of MO hashkafos like zionism and torah u’maddah etc. Some might say, no torah or maddah.
MO machmir means you pretty much act yeshivish, but you DO hold of MO hashkafos like zionism and torah umaddah, etc. They are known for the mitzva of hajj, the annual pilgrimage to the SOY sefarim sale.