That prevents timestamps, which isn't what we want. We want to have timestamps, but due to how echo works with a custom timestamp, you can get double timestamps on any of the lines you echo. Basically, it shows once in the channel and twice in logs.
If you remove timestamps from logs, then you have to manually add the timestamp to everything and not just echos. For example, let's say I'm customizing QUIT messages, so I use echo with a custom timestamp with that. When logged, it logs the normal timestamp AND the echo'd timestamp. If I don't echo the timestamp, it will only log once, but there won't be a timestamp appearing in the channel itself. If I turn off log timestamps, then only the echos will have a timestamp in the logs unless I echo every single line with a custom timestamp.
Right now, if logging is off, it won't log timestamps unless your script (echo) displays it even if timestamps appear in the window. If logging is on, it will insert a timestamp in the log regardless of what's on the screen, which means that you get the double timestamps if you echo a line using a timestamp.
What I'd really like to see is logging that matches what is seen in the window being logged. In other words, if you have timestamps appearing in the window, then it will log those as they appear. So... timestamps turned off in logging options will not add timestamps if they aren't shown in the window, but if they are shown in the window, it will still add them because the window is requesting that timestamps be seen. It won't insert timestamps on a line that doesn't have one in the window, but will display it exactly as seen in the window. If timestamps are turned on, then it would always insert a timestamp no matter what (as it does now).
If anyone thinks the timestamp off option I suggested would be a problem for people, then a third option for "Timestamp using window settings" or "Timestamps match window" or something that will do an exact log of the lines including whatever timestamps are shown on the line (whether manually added with echo or automatically added based on the timestamp lines option).
I think most people who want timestamps would like a 1:1 log of what they see on their screen without ignoring automatic timestamps and inserting new ones, which is what happens now.