This is strange. Your version was 4.0.2.2 and when you try to installed 4.0.5.x it recognized your current installation as 4.0.5.2, so it gives you an info if you would like to downgrade! then you need to uninstall previous version before downgrading. This is logical. Downgrading can be a problem, so uninstall is required. Don’t know why your current installation was recognized incorrectly (maybe some kind of bug or you really already had 4.0.5.2 in the first place).
In general on Windows if you install 4.0.x and are upgrading to newer version then you don’t need to uninstall LibreOffice first. See this web page for more info: https://www.libreoffice.org/get-help/installation/windows/ where is a statement:
You do not have to de-install any previously-installed version of LibreOffice. If you do have an existing installation of LibreOffice, all your preferences will be preserved and that old installation will simply be overwritten.
If I remember correctly the only exception was LibreOffice 3.5.x to 3.5.y migration where uninstall was required due to a bug in LibreOffice. So this was exception that was solved few years back.
A word about 4.1.x - this is latest stable version, but can be more buggy then currently extra stable 4.0.x. So if you are enterprice user I would suggest to use 4.0.x, if not then you can install 4.1.x and if some problems appears report them at bug tracker.