Yes, it does seem very odd that the tech would insist it doesn't have a viscous coupler. I don't know what the difference is between the NP119 and the NP129, perhaps captspillane will be on later to give you advice.
The tech obviously doesn't have a clue. The "9" means viscous coupler. That is why a 119, 129, 229, and 249 all must have viscous couplers. Of those its only the 249 that isn't an identical interchangeable unit. The 249 viscous coupler is very different than the earlier transfer cases.
The first digit is the number of speeds, in other words a "1" doesn't have low range and a "2" does. That has always been true.
The second digit changed in meaning, but in the newer generation of transfer cases it is an approximate strength rating. In other words a 241 is stronger than a 231 but not nearly as strong as a 271. The only expection to that is our transfer cases. In the early 119, 129, 128, 229, 228, 219 cases the second digit tells whether the transfer case has a 2WD function. In other words a 129 can be made into a 119 by eliminating the 2WD function and it can be made into a 229 by adding the low range components.
A "8" for the last digit means it has an open differential only. The 128 and 228 transfer cases were totally identical to the 119 and 129 except the Viscous Coupler was eliminated. All your 1986 Eagles and Jeep trucks had those. Your 129 transfer case will behave exactly like a 128 if your viscous coupler doesn't have any fluid in it, which isn't a bad thing. You won't notice the difference unless under extreme circumstances.
Other popular third digits are "1" to mean fully locked outputs in 4WD. They are often called "part time" cases because they can't be left in 4WD on dry roads without damaging the transfer case. This includes the XJ 231, Rubicon 241, and the beefy 271 found behind the Ford 7.3 diesels. "2" as a third digit, like the Jeep 242, means that it is a torque biased open diffential transfer case. It is called a "full time" case because it can be left in 4WD on dry pavement. It also has a fully locked "part time" mode. "7" as a third digit, like the Grand Cherokee 247, is a limited slip differential. This is the modern version of a viscous coupler. It lasts longer, responds faster, and doesn't use the toxic silicone fluid. The 247 replaced the 249 because viscous couplers are considered obsolete.