This thread got me curious so I went back to my PADI OW manual (1990) and my daughters (2016j to see if there was any difference in ascent procedures. There are a few subtle changes.
1990
1. You and your buddy should signal each other that you agree to ascend.
2. Note the time of your ascent. If you do not have a watch, simulate checking the time by looking at your wrist.
3. Extend one hand over your head for protection and put your other hand on the BCD exhaust valve control.
4. Look up and around, slowly rotating during your entire ascent.
5. Swim up slowly, at a rate no faster than one foot per second, while breathing normally.
2016
1. Signal “up” and confirm your buddies are ready.
2. Check your dive computer to be sure you are within its limits. (You’ll learn more about these limits later. If you’re not using a computer, check the time for use with dive tables)
3. Look up and hold your BCD deflator hose. Do not add air to your BCD, if you’re properly weighted and neutrally buoyant, you only need to start swimming up gently.
4. Ascent slowly-no faster than your dive computers maximum rate. The maximum ascent rate is ...60 feet per minute, but most dive computers require a slower rate of ...30 feet per minute. Most dive computers will warn you if you ascend too fast, so use your computer to guide your speed. Release air expanding in your BCD to control your buoyancy so you don’t start to rise to fast. If your not using a computer, use your timer and depth gauge to be sure you ascend no faster than ...10 feet each 10 seconds.
5. Look up and turn as you ascend, and stay with your buddies. Watch for obstacles overhead. Reach up as you near and break the surface.
There are some obvious changes in the two procedures, emphasizing the use of a computer. But there is also a subtle change. In 1990 you were encouraged to ascend vertical by the verbiage to “extend one hand over your head” from the beginning of the ascent whereas in the 2016 version you are told to look up during the ascent but not necessarily extend a hand over your head until you begin to break the surface.
If could be innocuous but I would interpret the change as being more neutral about body position while ascending IOT allow multiple methods. Interestingly the pictures in both manuals show divers ascending in vertical positions, but the 2016 version shows the diver holding and looking at computer during ascent rather than having hand extended overhead Superman style.