This is true. Like I said earlier, it's much more effective to look at other things that may not be so obvious right off the bat. Going for things that are less obvious to check for makes it more difficult for the client devs or skidders to patch.
There are various detections that I'm not going to go into detail on a forum, but I will share some of the more obvious ones that are also easily bypassed, but also are much more effective and less of a nuisance to the player.
1. Post-attack check. Unfortunately, this check only works for versions 1.8x and below. 1.9+ stopped sending the Flying packet, which is sent every 50ms. We need this packet to use it as a timestamp to see if the player attacks before or after the Use Entity packet.
2. KeepSprint check. This check can be very effective against combatting killaura and the overall effectiveness of it. Basically, when you hit a player, you decelerate slightly. If they don't decelerate, they are cheating.
3. Strafe checks. Most auras surprisingly don't move correctly relative to where their head is looking, this can be because of silent rotations and such. There are only 8 valid directions you can go playing on a mouse and keyboard. If they go any other direction, they are cheating.
4. Hitbox checks. Although it may not be obvious since killauras aim usually, otherwise they will be flagged by another check, most auras actually hit out of the hitbox, which is quite funny. You can flag this by seeing if the player hits outside of the hitbox.
That's all I have for you guys. I don't want to let too much information out there, that's why I only shared the methods that are very well known.