My car is still up on blocks so I went out and took a look to refresh my memory. The resulting discussion is a little long, but there are some somewhat realistic ideas that the end that my help.
There is a port for a bleeder valve in at about 1:30 to 2:00 as you look at the slave cyl from the front. As I remember there was nothing in this port on the new slave cyl and I had to transfer what was on the old slave to it.
This part I tranfered over looks like it could be a bleed valve on the end, but being shaped just like a bolt head (hex) with a hole in the center I saw no way to get a good seal on it with a hose for bleeding, so I assumed it must not really be intended for that and took the chiltion's advice on just pumping the pedal.
The slave cylinder was dry (unless it was primed by the manufacturer, though I would think it would have leaked a little in the box), and really it should not have worked since the line does not come out of the top of the slave cylinder. The only thing I could begine to guess at was that the device that screwed into the bleeder port (I say 'device' because with a multiple piece, 3/4" dia body about 2.5 to 3" long, it looked like more than just the simple extension/pipe that would be needed to simply move the bleeder out to hole in the bell houing) was some sort of fluid sensitive check/float valve that would let air but not fluid out. It's conceivable, but I'm not sure that the cost of such a device would be justified simply by the time it saved on the assembly line. I would also doubt that such a device would work on my car after 136k
With all this said I here's another thought on something to check. Having never had the master cyl off of this car I'm not sure if this is the case, but many master cyls for clutchs have an adjustble link to the pedal. If that link is adjusted too long (or the pedal is not coming up al the way for some reason) it will not let the piston in the master cyl come back far enough to uncover the hole that leads to the reservoir. If there is not good flow from the reservoir the fluid will become airated with repeated bleeding attempts at bleeding. Reverse bleeding would not be componded by this problem, though it probably would not be effective on these cars anyway since you're trying to push air out the line which is half-way down on the master cyl.
One solution might be to pop the line off of the slave, fill it with a reverse bleed gun, (from the clutch line port, with whatever bleeder you have cracked), close the bleed, reconnect the clucth line, and then carefully reverse bleed without* getting any air from the reverse bleeding gun/pump back into the slave. *This may be next to impossible.
Here's one other thought, going back to the idealistic solution of pumping the pedal. Is your car level when they are trying to bleed it or is it up on one side?...may make a difference if the system was designed to be 'pumped out' by a someone on the assembly line while the car rolled along. When I 'bled' mine while all four corners were up with the car level.
Good luck, the best you can hope for is for the person who bled these things out at the factory to contribute to the discussion, though that person may point you to the person who designed the system...perhaps while muttering some choice words.