Infect plays Treasure Crise rather than Become Immense?
Why wouldn't they? They already have plenty of free and one G costing pump spells, their big down fall is removal in response to pump, so drawing more cards, especially off their burned pump is perfectly fine.
In short, the extra pump spell doesn't seem good enough, but I could be wrong.
Edit: The other issue is that Become Immense doesn't really give you more benefit than say Invigorate or Might of Old Krosa, being that Invigorate is the best option since it's free and dodges most counter magic, the difference between +6 and +4 becomes very minor, so drawing 3 is massively better in that situation.
As in two hits with +4 are a kill, just like two hits of +6 or +6 and +4 on a one power guy.