Many of the toolpath strategies in HSMWorks are projection based; often in multi-axis milling, the optimal toolpath projection angle won't work as the tool axis. Allowing these to be defined separately would make for a much more flexible 3+2 environment, as well as go a long way toward making the existing simultaneous tilting options more viable.
Probably the most universal usage case for this is for better toolpath generation when you're axis limited, but it has further reaching implications for multi-axis stuff as well. If nothing else, look at it like this.
we're all fairly used to this situation, a parallel toolpath applied to a fillet. Stepover is massively inconsistent; yes, it would be great to get a constant scallop version instead, but this is what we've had.
Ignoring how simulate glitches with indexed stuff, this is the same operation but calculated on 45*. The important bit to pay attention to is the contact point, in this case, the toolpath is MUCH cleaner, scallops are more even, as we've effectively turned a surface that used to have 90* of transition into one with 45* of transition. If you pay attention to how multi-axis paths (specifically, contour + multi-axis tilting) calculate, they effectively do the opposite; generate toolpath from a fixed orientation, figure out the tool-axis needed to avoid collision, and correct the toolpath to the new orientation while maintaining the contact point. In this case, i'm looking to do the same, but rather than correcting to a varying tool axis based on where it collides, just let the user choose the orientation.
In simple 3+2 stuff, this often poses additional issues; Often, a tools axis selection will be limited by other limiting factors, primarily where it can fit without collision. When tool axis is limited as such, the issue becomes projecting a toolpath into an area with high slope, and the vast majority of AutodeskCAM toolpaths, being projection based, don't deal with extreme degrees of slope well..