It is impossible to be 100% right, but I would think you should have no problem. I'd go at least 85%/15% that you could use a sharpshooter shovel, straight down at the edge of the liriope and not hurt your Sky Pencil much. Fill it back in with soil that matches the consistency of what was there. 'Course, remove mulch/debris first.
Take it from me, I have used glyphosate on Liriope muscari and L. spicata (spicata should be called L. sativa meanus nastiius never-useus!) Digging the starts returning from roots in the ground is much more effective than spraying. I use glyphosate on many spot weeds, but dig liriope.
hortster

The "sky pencil" (silly I know) is fairly young so dig it up and remove runners of the unwanted grass from its roots. Then dig over the whole bed removing the "monkey grass" (silly I know) and replant the Japanese Holly (Ilex crenata). Job done.

What would be the problem with letting the Ophiopogon simply act as a ground cover throughout the area? There is certainly no real issue of the plants being in conflict with each other's roots for best growth. Or is this a case of an aesthetic preference for keeping bare earth between plants and never letting one touch another?