Are SMART offline data collection and offline attributes obsolete?

**TLDR;** I tried to understand the difference between SMART Offline and Always attributes, and thus to understand what SMART offline data collection is, and if I should enable it on my HDDs. smartmontools' official wiki states that : > Note that the SMART automatic offline test command is listed as Obsolete in every version of the ATA and ATA/ATAPI Specifications. (...) However it is implemented and used by many vendors. After some extensive reading on the web, and also some tests, the conclusion I reached is: - Nowadays SMART offline data collection is obsolete - All data is updated in real time (e.g. Offline and Always attributes behave the same way) - There is no need to enable "Auto Offline Data Collection" (# smartctl --offlineauto=on /dev/sda), nor to ever launch it manually (# smartctl -t offline /dev/sda). - As for the reason all this offline stuff is still in smartmontools, it's probably to keep it compatible with some very old HDDs that indeed implemented real offline attributes. Am I right ? Or do I miss something ? ---------- **MORE DETAILS** I did some tests on a HDD, which has 3 offline attributes (and has Auto Offline Data Collection disabled):

# smartctl -a /dev/sda
(...)
Offline data collection status:  (0x00)    Offline data collection activity
                    was never started.
                    Auto Offline Data Collection: Disabled.
(...)
240 Head_Flying_Hours       0x0000   100   253   000    Old_age   Offline      -       235 (114 97 0)
241 Total_LBAs_Written      0x0000   100   253   000    Old_age   Offline      -       13381561756
242 Total_LBAs_Read         0x0000   100   253   000    Old_age   Offline      -       20472945077
(...)

I then wrote some data on that drive, and noted that all 3 attributes were updated in real time. Thus, they are in fact online (or Always) attributes, and not Offline ones. I did the same test on a few other HDDs, the behavior was identical.