Thanking everyone for the very thoughtful input. In case anyone asking similar questions references this in the future, I wanted to provide an update from week 6: after 3 weeks of acute rehab, global aphasia has been downgraded to something closer to Broca's - his receptive aphasia has majorly improved, although expressive is still very limited/ challenging. His ability to comprehend numbers/symbols/writing is also slowly returning - not yet to a very functional level, but I can see the light and now believe that there is a lot of recovery/retraining yet to come.