[racket-dev] info.rkt `deps` and new #:version keyword: Backward compatibility?

After I gave my Frog talk at RacketCon, in which I said a goal of Frog
was to make it easy to install, J. Ian Johnson tried to install it...
but couldn't.

As best I understand, it's because he was using Racket from HEAD, and
at some point recently the `deps` expression for info.rkt changed for
the case where you specify a version. A case which I've been using
(recent versions of Frog need a >= version of Markdown).

For 5.3.6 and (until fairly recently in HEAD) it was:

# frog/info.rkt
#lang setup/infotab
(define version "0.7")
(define collection 'multi)
(define deps '(("markdown" "0.5")
               "rackjure"))

But it recently changed to require a #:version keyword, therefore it
would have to be IIUC this for 5.3.900.???+:

# frog/info.rkt
#lang setup/infotab
(define version "0.7")
(define collection 'multi)
(define deps '(("markdown" #:version "0.5")
               "rackjure"))

But that wouldn't be compatible with 5.3.6 IIUC.

As a result I would have to maintain two different packages, one for
5.3.5 and 5.3.6, and another for 5.3.900.???+ and greater (yuck).

Until now, even the major change to single-collection defaults was
done in a way that preserved backward compatibility (well, after
taking action to add `(define collection 'multi)`, but after taking
such action the same info.rkt works for old and new).

1. Am I understanding it correctly?  (Not a rhetorical question; I
have a lot of "IIUC"s above.)

2. If so, is it really the intent to break backward compatibility?

3. Instead couldn't the #version keyword simply be optional?