There is nothing wrong with a front shoulder shot on a buffalo with a suitable calibre as the lungs, arteries and/or heart may also be damaged.

Same with a spine shot especially to the neck. May kill outright or incapacitate the beast. The danger with a neck spine shot is missing the spine, as the buffalo may escape, perhaps with a painful and serious injury.

I too have read in books where for example in very thick jungle the hunter has taken a rear hip shot on an elephant (all that he could see) to drop it, and then additional shots to kill it. I do not think that is appropriate in sporting hunting, but if the elephant was a man killing rogue elephant and not hunted for sporting purposes it might be justified under different criteria.

Generally though an "anchoring" shot in sporting cicumstances should only be taken if an already wounded dangerous beast may escape. It is better to anchor it quickly then if no killing shot is immediately available.