This drives me nuts , has done for yrs.
Imagine a letter T formed of two lines, select InterpCrv and choose start tangent by hitting S and enter.
select the junction of upright and cross lines, wishing to head eastwards, instead it wants to start downwards.
Turn off END and use Int and still it wants to go downwards following the upright of the T shape.
I wish it said Direction and one could choose which curve to follow, or even ignore the curve, if the entire T is at an angle and I want to go due east !
It insists in following a line and 99% of the time not where you want.
I have to turn lines off to use it.