Also I think this is all quite a good example of the “play of formulas” idea:
"And how is the heart’s release by love developed? What is its destination, apex, fruit, and end? It’s when a mendicant develops the heart’s release by love together with the awakening factors of mindfulness, investigation of principles, energy, rapture, tranquility, immersion, and equanimity, which rely on seclusion, fading away, and cessation, and ripen as letting go. If they wish: ‘May I meditate perceiving the repulsive in the unrepulsive,’ that’s what they do. If they wish: ‘May I meditate perceiving the unrepulsive in the repulsive,’ that’s what they do. If they wish: ‘May I meditate perceiving the repulsive in the unrepulsive and the repulsive,’ that’s what they do. If they wish: ‘May I meditate perceiving the unrepulsive in the repulsive and the unrepulsive,’ that’s what they do. If they wish: ‘May I meditate staying equanimous, mindful and aware, rejecting both the repulsive and the unrepulsive,’ that’s what they do. The apex of the heart’s release by love is the beautiful, I say, for a mendicant who has not penetrated to a higher freedom. "
The above clearly mixes several sequences that cannot be right; the Appamāṇā cetovimutti is already a graduated sequence culminating in upekkha so it is nonsensical to say that the first step in the sequence can be practiced with the awakening factors, which is another graduated sequence culminating in upekkha, so these are 2 formulas being combined here. I think reading between the lines the “perceiving the repulsive” sequence is another such sequence, again culminating in equanimity, so in this sutta we have at least 3 formulas, the immesurables, the awakening factors and the repulsives, and all of these are used in a sutta that attempts to link the immesurables with the formless attainments, gosh.