BLO is a very mild accelerant as well as a lubricant (IMO) that helps smooth the CA going onto the pen. When applied to the paper towel first, BLO (again IMO) prevents so much of the CA from being absorbed into the paper towel and puts more onto the pen.
However, I use holly and bloodwood quite a bit. BLO will cause holly to look like antique ivory quick. It will turn bloodwood from a brilliant maroon/red to a slightly burnt orange brown, so I don't use BLO at all - at least on the first few applications of CA on these woods.
I do use BLO directly on the wood of most other blanks because it enhances the grain and color immensely that CA does not.
There are times when BLO enhances the grain and chatoyance as well as bring the colors out more beautifully. The difference is knowing the wood and knowing finishes. Clear water based, acrylic based and some lacquer based finishes (including CA) usually set a neutral tone to the wood when applied directly and before ANY oils/BLO. ON some this looks great, but on other it leaves it uneventful, too clear and even plastic looking.
BLO, Poly's, and other "oil" based finishes add a "warmth" to the surface that is greatly appreciated in most circumstances. BLO does this, but it (and the other finishes) also tint white woods to slightly yellowish or red woods to orange-ish. It is a matter of knowing your woods and how you want them to look.
With this in mind, your application of CA/BLO, BLO/CA will change depending on the outcome you want as it relates to color.
One thing to avoid - don't use BLO directly on oily woods first or the CA will have a tendency to "lift" or not stick.