Well from time to time comic books have bein vary contradicting to what characters abilities can do.
But lets all cut thru the BS.
Crossover matches do not count since there are non canon.
What If’s do not count, for the same reasons.
And since I establish non PIS/CIS rule in this match. Lets avoid the anything realated to non canons and What Ifs? Ok?…..
Now no BS
LT - Is a cosmic entity that governs all of the muliti -verse to maintain a balance of order as it see fit.
PF- Is a cosmic entity that can bring out the destruction, and recreation at a multi - verse scale level as it sees fit.
According to X-men Forever during each creation cycle LT and the abstracts get replaced by an evolved humanity. Phoenix is the force which co-ordinates and fuels this process and it keeps the creation cycle going on forever Big Bang after Big Bang. While the abstracts are reflections of the universe and their roles can be usurped and re-allocated at any time during the creation cycle (as we've been shown previously on panel via the IG saga for example) Phoenix is a constant throughout.
In X-men Forever Stranger found out about this destined replacement and decided to try and access the Force via Jean in order to bring it about prematurely and on his terms. He would use the power to speed up the evolution process, collapse reality, but protect himself during the turnover allowing himself to emerge in the new reality as the supreme being.
To help him bring this about the Stranger infiltrated the systems of Prosh the Celestial Ship (Prosh served as X-factors transport in the past so Stranger knew they’d trust him) and programmed him to gather Jean and a group of mutants who represented key features of this evolutionary process. Prosh however was loyal to his mutant friends and tried to help them out by sending them through time to key points in history in an effort to warn them of the Strangers plans. Something he couldn’t do directly because of the programming:
When Stranger was discussing his plans with Jean Eternity secretly interrupted and unbeknownst to Stranger told Jean that while it was true that the fundamental forces were replaced each creation cycle, it was a part of the natural order which they encouraged, they weren’t against it as the Stranger had thought. He then told Jean that Strangers plans must not be allowed to come to fruition.
If TOAA is truly the supreme being (something has only been hinted at not conclusively shown) then if Phoenix co-ordinates LT's replacement as part of the natural order well i'll leave you to make your own conclusions.
Either way its what happens naturally and the fact that the power can be employed to pervert the process and bend it to a persons will says it all.
If Phoenix does it as part of the natural order who's to say that it doesnt work for Marvels supreme being as has been suggested on panel.
Another thing to remember about TOAA is that all that sbeen said about him/it is that its a being above gods and it has greater power than the IG and Eternity. Many things do. Its never actually been stated that its Marvels supreme being, only suggested. Therefore its not canon.