That certainly is a 90 degree knot. Others may opt for using a long tag end on their mono leader swivel knot using a clinch or trilene knot which are also close to perpendicular 90 degree knots. Where I'm at on the west coast, schoolie stripers and large perch overlap around late Feb-early Apr. which means I'm using a fairly light outfit and also need flexibility in switching back and forth between the two. Now 25-30 lb may not seem like a light-ish leader, but if you use a standard dropper loop for attaching leaders, that is a 60% knot. Catch a couple fish on the teaser and that knot is now 50% or lower which means 15 lb or less. Knots like the clinch, improved clinch, or trilene.(I'm a big fan of improved versions of the trilene, btw) are pretty decent in one direction of pull. Catch a couple fish on the teaser tag or heaven forbid, that rodeo known as a double and break strength is unpredictable. Dilemmas such as this cause those of us who suffer from OCD many a sleepless night.
I apologize for the really crappy photos so I will attempt to describe what I was trying to display. My schoolie setup uses a a stainless steel ring, 10 lb braid and 30 lb. Big game mono. What is shown in the attempted photos is my perch setup with 6lb braid and 25lb. Big Game mono on a stainless steel 3mm tippet ring. The knots used (for lack of any meaningful descriptor) are Galen knots. (Designing and testing knots is somehow therapeutic for my OCD Helps me sleep better) The main thing I was trying to convey is to limit the ring space/size so that the loop on the teaser leader is limited and stands out at 90 degrees. I don't want the main leader knot or the main braid knot to slip around so I fill the off side space by winding the braid tag end around the off side of the ring. The most important part is probably the way the teaser leader is attached. You want to attach it to the bare metal portion of the ring. Insert the loop through the ring. Instead of passing the teaser leader directly through the end of the loop, pass the end of the loop back through the loop before passing the end of the teaser leader through the loop. Repeat this one more time and you have a kind of cat's paw weave kind of thing going on which helps it stand off at 90 degrees very nicely to prevent tangles. The rest of the setup employs a variety of Galen knots but that addresses a whole nuther set of issues and reasons. I like the flexibility of this set up because it allows me to quickly go from plug/jig and teaser to Carolina style perch fishing. Hope this helps.