You are correct
The Overall Length (O.A.L.) most people are referring to is sometimes referred to as the Combined Overall Length (C.O.A.L) by others. The C.O.A.L is what most on this forum mean because it is the length of the entire round from base to tip of the bullet. This C.O.A.L. dimension is important in magazine fed weapons because the C.O.A.L can exceed the internal dimension of the magazine and still be fed into the rifle.
The O.A.L can be measured using a bullet comparator (Hornady Lock-N-Load and Sinclair both make them) that bases the length of the round on the distance from the base to a consistent diameter point on the ogive of the bullet. This O.A.L. measurement makes for a more consistent distance for the bullet from the point to where the bullet will engage the lands of the barrel, keeping the "jump" or "lead" of the bullet the same from round to round.
The O.A.L can also be set using the bullet comparator and tends to but not always keep you within the margin of length necessary to get the round to fit the magazine.
In a nut shell, the best and most consistent means of measurement will be the O.A.L using a bullet comparator and as long as you keep that dimension withing the length of the magazine, you'll have no problems at all.