If the number of devices is set to a minimum of two, the license will work for both the Windows and Android versions of Adguard and can be used simultaneously. Both versions of Adguard (along with the upcoming Mac and iOS versions) will use the same license regardless of platform providing the key you have is set to the number of devices you need.
delete (or rather move) this in case it is OT but IMHO Adguard needed to adapt the EULA then.
The EULA says "2.1. You may install and use the Software on such a number of Computers that was specified when You purchased the License to the Software." which I followed by using AG in proxy mode (the software is installed and used on the single proxy server, not on the android device).
It also was IMHO fair to clearify that in normal speech (like "each computer/device whos internet traffic is filtered by AdGuard needs a single license").
Especially as AdGuard has a builtin proxy itself!
P.S. I only can 'judge' about German legal issues (but often EU legals are equal), over here I was not violating that paragraph by using 1.000 devices over a proxy paying a single license.