Decompression is not an exact science and using exact measurements of depth and time don't change that though it does create the allusion that we're being precise.
Using some decompression software, run some multilevel dives. Then run the same dives using a time weighted average depth and see how the software output varries. You'll find that the variations are very small, likely much smaller than the accuracy of the model. Once one has that "profile depth", whether from true multi level model calculations or rule of thumb methods the way you conduct the ascent is what makes the difference. To prove that to yourself, look at a software that applies gradient factors toa neo-Haldanian model. Notice that modifying the gradient factors effects the output far GREATER than minor variations in depth and time.
So some questions...if you were to dive using that software, which is the correct gradient factors to use? If I estimate profile depth, does it have a lesser than or greter effect than modifying the gradient factors (which most would view as lagit)? Even using a table, which is the correct table? Even if we only consider recreational dives, notice the huge variation in NDL's. Buhlman gives an NDL of what...17 minutes at 100 ft? DSAT 20 minutes and other tables maybe 25? That's an 8 minute difference which is 47% of the buhlman NDL and 40% of the DSAT NDL. Now notice that when gradient factors are applied the 17 minute 100 ft buhlman dive will require some decompression. What does that say about your 20 minute 100 ft DSAT dive? Which is the reaL NDL? You could see as great or greater differences in the outputs of different computors. If this were any kind of an exact science we would only be able to use one of these tables, one set of gradient factors or one of these models.
What I'm recommending here is a learning excersize and not meant to convince any one to change the way they dive.
Psonally, I think divers are just kidding themselves into thing that carrying a computer than does thousands of calculations per second is doing anything meaningful for them. I think we're applying the precision to the wrong end of the dive. That's just my opinion but I haven't been bent yet...except for maybe some subclinical stuff when I used to strictly follow tables and computors. LOL For the record, the longer and deeper I dive the more I want to be making the decisions myself rather than relying on the 22 year old CS major (who doesn't dive) who wrote the firmware in some cheezy (but expensive) computor.
