FWIW, THE reason why, as far back as 2002 at least (as far as I can tell: http://web.archive.org/web/20020810044317/http://www.michaeldresdner.com/dres10.shtml
), people combined CA and BLO for two key purposes:
1) The BLO DOES cause the CA glue to set faster (as is much the case with anything you blend into CA glue, which is why I was confused earlier in the thread!) Go back a literal 20 years to 2002 (which based on some things I've found, was close to the dawn of people using CA as a pen finish), and BLO was a great "accelerator" for CA glue! Because BLO acts like an accelerator, those who seem to truly understand the BLO+CA finishes usually recommend using a very slow setting CA glue, to give yourself time to properly apply the finish. One of the more informed approaches I came across was this:
2) The BLO and CA seem to cross-polymerize with each other, the fatty acid molecules of the linseed oil combining with the synthetic molecules of the CA to create an entirely different kind of finish, one that (according to the people who really seemed to know what they were talking about and doing) was more flexible than CA but just as durable, and highly glossy.
Many of the resources I've come across proclaim that because we now have "proper" CA accelerator spritz or sprays, we no longer need BLO, because the only reason it was used was as an accelerator for the CA. IMO that is only half correct, as the other reason people used BLO was because it created the copolymer finish that was highly glossy, and more flexible than CA, making it a bit more resilient.
To the original poster:
One of the things I've found to be consistent among those who get a very high gloss finish with BLO+CA, is they sand their blanks to the point where they are already shiny before applying the finish. In the link above, he micro-mesh sands his wood to 12000 grit before ever applying any CA or BLO. I have found the same fundamental to be true in my own explorations of finishes...when the wood shins on its own, then the subsequent finish is more likely to support a highly glossy result. If I stop sanding at 400 or 600 grit, then it is often a lot harder to get a super shiny result.
There are also two ways I've heard of the BLO+CA finish being applied to high gloss results. Either with a dollop of BLO in a paper towel, followed by a dollop of CA, which is then immediately and quickly applied to the spinning blank...or with two separate rags or paper towels, one with CA, one with BLO. The CA is applied first, quickly followed by the BLO, with both being applied simultaneously, with the BLO coating the CA and reacting with it to create that copolymer. In either case, the CA is the first to touch the blank, but the BLO follows very quickly and as far as I can gather, is blended into the CA while the finish is being applied. The BLO accelerates the CA. The result of each coat should be a smooth, shiny finish.