You can try ignoring early media to force the A-leg to answer before anything else happens. Try this and let us know if it does what you want:
originate {ignore_early_media=true} sofia/internal/
1001@192.168.46.15 4600
You can probably look at the SIP traces of the two options you've tried (without ignoring early media) to confirm that you're getting media prior to answer when doing "originate sofia/internal/
1001@192.168.46.15 4600" - probably in one case you get a 180 and in the other a 183. Check it out and let us know. :)
-MC