It says 33.5" but that's just what I mean. Mayo just said 32 inches, then Manx said 32 and 7 8ths, then CBS says 33.5 inches. It's all over the board and those are pretty big differences.
It's not that uncommon for prospects to measure slightly differently at different venues, even in the height and length measurements, which are slightly subjective. It's easy to be off half an inch or so in where you're starting to measure arm length, for example.
As for Armstead, his Shrine Game measurements a couple of weeks ago included a reported height of 6'5" and arm length of 33 1/2":
East West Shrine Game Measureables | National Football Post
Armstead was a late addition to the Senior Bowl, so his weigh in results occurred later than most participants, and weren't in the original reports. But subsequent reports were that he measured at 6' 4 3/4" with an arm length of 32 7/8":
Senior Bowl Weigh-In Results, NFL Draft - DraftCountdown.com
Draft sites such as CBS only use measurements from one of the "official" events, so that further augments confusion. Armstead will get measured again at the NFL Combine, which may differ from both of those, and which will probably be used as the "official" measurements. But these are close enough. It seems like Armstead is around 6'5" or a hair under in height, with an arm length of around 33" give or take a tiny bit. I remembered "32 +" from the NFL DraftCountdown report, and used "32", which is probably too low.
It seems like Armstead's arms are a bit on the short side for his frame and certainly not ideal, but not egregiously short to the point where they would be a huge red flag. But on the short side. Brian Bulaga had an arm length of 33 1/4" at a height of 6' 5 3/8" at the 2010 Combine, and he's played more guard than tackle, though there is talk of Green Bay moving him to left tackle in 2012. Riley Reiff also weighed in with 33 1/4" arms last year at 6' 5", causing a number of teams to question whether he would be better suited to guard than to tackle. Both Bulaga and Reiff were touted as possible top-10 picks, and both fell to the early 20's based in part on their arm measurements and concern about where they projected. So I don't think it's unreasonable to question whether Armstead projects better to guard than to tackle. Garrett Gilkey, at 6' 5 7/8", had an arm length of only 31 3/4", which is extremely short, suggesting that he's probably a guard only in the NFL.