Closed source OSes are such a bane.
It's actually not. As a user I'd expect the device to wake up and still have the same IP address via a continuation of the lease.
Yes, the correct way would be a longer lived DHCP lease, but el-cheapo ISP routers often lock down such settings.
When I put a machine into standby, I want it to go in a standby state, and then stay there until I explicitly wake it -- not keep doing whatever background tasks the OS developers, app developers, or whatever other third parties think they need to keep doing.