It was discovered that cutscene movement is possible in more scenes than the ones previously mentioned (elevators on M4, M5, M7, M14, M12 Geryon defeat, M17 spike room). The reason this could be relevant is not just being able to save some time moving, but if the IGT doesn't run during these scenes, ILs will be heavily affected by this. The full list (not including possible ones in secret missions or areas not relevant to speedruns) is this:
M3
After activating wheel (blue door hand disappears) scene
M4
Chamber of Echoes, Living Statue Room Enigma pre and post scene, elevator going up scene, Incandescent Space pre and post scene, Chamber of Echoes scene, Endless Infernum 1st & 2nd scene, Gigapede enter & defeat scene
M5
Post Bloodgoyle scene, Jester pre and post scene, Giantwalker Chamber post Jester, post Astronomical Board scene, using Vajra scene, pre & post Living Statue Room scene, using Soul of Steel scene, elevator wheel activation scene, elevator going up scene, A&R combination scene
M6
Trial of the Warrior pre and post scene, Artemis scene
M7
The Divine Library pre and post scene, Tranquil Souls pre and post scene, elevator going down & up scenes, Chamber of Echoes fire door scene, Cursed Skull Chamber wheel activation scene & pre and post scene, Tranquil Souls post scene, Peak of Darkness scene
M8
Tusk scenes, Gigapede scenes, Ignis Fatuus pre and post scene, Leviathan pre scene
M9
Rotating Bridge scene, Provisions Storeroom pre and post scene, Subterranean Garden pre and post scene, Subterranean lake scene, Provisions Storeroom (2) pre and post scene
M10
Stone Mask scene, Rounded Pathway pre and post scene, Provisions Storeroom pre and post scene, Rotating Bridge scene
M11
Altar of Evil Pathway scene, Altar of Evil pre and post scene
M12
Torture Chamber scene, Altar of Evil pre and post scene, Marble Throughway pre and post scene, Rotating Bridge scene, Geryon defeat scene
M13
Effervescence Corridor pre and post scene, Vestibule puzzle solve scene, Orihalcon scene
M14
Elevator going up scene, Altar of Evil pre and post scene, Hell's Highway scenes
M15
Upper Subterranean Garden post scene, Gears of Madness pre scene, Altar of Evil Pathway pre scene
M16
Chamber of Sins post scene, Living Statue Room pre and post scene, Waking Sun Chamber Golden Sun scene & pre and post
M17
God-cube Chamber scene, Trial of Wisdom pre and post scene, Trial of Skill pre scene Skull Spire pre and post-scene, Doppelganger post scene
M18
Chess boss pre and post scene, post boss scenes
M19
Room of Fallen Ones pre and post scene, Nirvana of Illusions pre and post-scene, Infinity Nirvana pre and post-scene
A link to this thread will be included in the rules for convenience's sake.