VirtualBox 5.0 Now In Beta, Adds PV To Windows/Linux Guests

[Markore]

It is not our responsibility to support third-party products. If something does not work by default in a product advertising simple use, it is a bug in that product, pure and simple; especially when it worked in a previous version of said product.

Simply setting ps/2 mouse in Virtualbox settings is working for your distribution that you want to advertise here.
Default VirtualBox mouse settings moved along and work fine for all supported systems.

If you have problem with default setting just change them for your distribution.
Not trying to test it and resolve for you is resulting in inaccurate conclusions.

Aether set it to PS/2 for your distribution or see what other distributions are using (probably you are lacking USB touchscreen support)
and try to implement it up to date like other OS distributions.
If you are not trying to resolve it for you, but just brag about it, it's just a waste of time.