That pretty much sums it up. The difference can’t be that stark, can it?
Yes, they are essentially synonymous – in fact, the usual definition of the negative sense of the verb “patronize” is “treat condescendingly,” and has been from the earliest citations.
As a side note – my 1895 Dr. Ogilvie’s gives a slightly ambiguous sense of “assume the air of a patron towards,” but this is in the context of more positive definitions, eg; “To countenance; to defend; to lend aid to.”
It seems to have drifted from a purely positive thing through perceived presumption or inappropriateness.
Very different words:
Alice: “I saw a ghost last night!”
Bob: “I’m sure you did.” (Patronizing)
Carol: “Only a fool believes in ghosts.” (Condescending)
The way I understand it, condescending is basically a bad form of being patronizing.
That said, in modern parlance, I think being patronizing is rarely a good thing.
I don’t know if I’d really consider that second example “condescending”. “Condescending” (to me) implies a degree of faux polite indulgence of the one being condescended to.
To me, “condescend” always implies that the condescender feels superior to the other person in some way, whether in intelligence, refinement, social status, etc. The sense of noblesse oblige.
On the other hand, you can “patronize” a person without feeling superior to that person. For instance, a wife may be unsure about how her outfit looks and ask her husband’s opinion. The husband will say, “You look fine, honey,” only because he wants her to get going, not because he cares about her outfit. That’s patronizing.
No, that’s self-preservation. 
I usually think of it like this: patronizing is when you treat someone like they’re smarter than you expected. Condescending is when you treat someone like they’re not as smart as they should be.
That’s brilliant.