i think i got the true pacifist ending without ever finishing the game normally?

ok so a while ago i posted here about not being able to finish the game normally because somehow it didnt work. i tried doing an in game reset, but flowey remembered and made me really confused, leading me to delete my save files (from my computer and from steam cloud) which allowed me to play the game normally again (i spared and befriended everyone possible), but after defeating photoshop flowey i got the letter from undyne and did the alphys thing. after that i gained access to the true lab (which according to the wiki can only be entered in true pacifist) i cant really recall what happened but it all added up to me doing the lost soul thing with asriel and when i was done, i was able to go to the surface and get the true pacifist ending?

does anyone know why that could have happened?