Plotting a route, even if it's a single jump route, the plotter and the FSD assume a full tank.
As you have already figured out, To make a jump at your current actual jump range, you need to have the target selected directly.
It should be, that that is not the case recently. My Asp Explorer has a jump range of 34.10LY when the tanks are full, and a bit over 36LY when they are low. I have had times (since 3.0 dropped, but I am not sure exactly when) when I have plotted a route (with tanks full), the plot has worked, only for the FSD to tell me mid-way along the plot that the jump exceeds 5 tonnes of fuel. The only thing I can think of is that the route plotter 'assumes' I will fuel scoop at the calculated 'fuel star', but I, being a cautious Player, scoop at every opportunity, so then, at a 'long' jump, my ship is now too heavy to make it.
If I am right I would hope that FDev can re-work the route plotter to either always assume the tanks are full, or to clearly indicate the Player should not fuel scoop until they arrive at the designated 'fuel star'.