vm.vmemory.size is introduced as below on what's new.
https://www.zabbix.com/documentation/3.2/manual/introduction/whatsnew322
https://www.zabbix.com/documentation/3.0/manual/introduction/whatsnew306

A new vm.vmemory.size key has been added to monitor virtual memory statistics on Windows.

On windows, the term "virtual memory" has multiple meaning and it is also used as a synonym to Page File on disk(swap).
Actually, on windows there is a settings named "virtual memory" to set the size of page file size on disk.
[System Properties] > [Advanced tab] > [Performance Settings] > [Advanced tab] > [Virtual Memory section]

I believe it would be better to changed it to other term to avoid confusion.

It is wrote as "Virtual space size" in the following manual.
https://www.zabbix.com/documentation/3.0/manual/config/items/itemtypes/zabbix_agent/win_keys
Windows-specific item keys

See:
https://answers.microsoft.com/en-us/windows/forum/windows_10-performance/physical-and-virtual-memory-in-windows-10/e36fb5bc-9ac8-49af-951c-e7d39b979938