I think it's quite a wise time to comment. We've just seen the RAF in relatively popular operations, and while it's still fresh with exciting pictures etc in circulation rather than a more stale stale of policing the skies when there is smaller chance of much happening it can do no harm to spell out some of the SDSR repercussions.
Importantly perhaps, he's not demanding money now, but sowing some early seeds that can be used to build later narrative for awareness in the build up to the comprehensive spending review.
nb. The Audit Bureau of Communications put Guardian circulation at 279,308 this Jan (about 150K fewer readers than Times, about 100K more than Independent) Alternatively it's the second most read newspaper website of the UK press according to the Press Gazette ABCe, falling behind only the Mail; doubtless no one at all will read the article.
Ill informed assumptions are great.