If this is what you’re asking… I don’t know of any concrete proof that kerogen can’t be generated via other processes, but oil is big business and scientists have been studying the link between oil reservoirs and their source rocks for decades. There is ample information suggesting that kerogen is derived from plants and little evidence (to no?) evidence to suggest another process that would create kerogen.

The only reason to need another explanation for the creation of kerogen is if you are motivated to disbelieve the most simple and widely supported explanation.