I don't have a "KBVT" in my FS9 install, but I'll guess you intended to go to Burlington VT (KBTV) and not Skagit County in WA (KBVS)just created a flight plan using low alt airways from KSLK to KBVT.
Here's my result from MSFS Flight Planner (basic choices) and with the manual addition of the BVT VOR. Both show the waypoints, freq. and altitude. Now, if you mean what gets output to the flightplan listing in the GPS, no.. there is no altitude. 1st and 2nd generation GPS generally weren't that sophisticated and did not have VNAV capability so altitude was redundant ( you'd have the printed FP anyway).There are no waypoints between, and the flight plan does not display the enroute cruising altitude between those two points.
Little typos can make for large navigation errors... I simply went to the flight planner, input the two airports, specified ( in the first posted attachment) Low Alt Airways and got what you see. For the second attachment I manually added the BTV VOR by dragging as I was always taught that a route should go to a primary navaid before terminating. I retried it using the IFR selection and got this (attached). As your map shows the LL airways it doesn't seem to be a corrupt database, but ... thinking... As an experiment you could try to do it again, and if you get the same result, before closing or saving, try to drag the route line out to either of the intersections to see if they will be recognized and the same for the BTV VORYes, indeed, KBTV. Pardon my typing.... You're getting different results, I think. If I use low airways only, I don't get the SLK VOR, nor any of the other intersections. Are these added by you, or is my flight planner failing?