I am able to ping a device on a different subnet without passing through a L3 device. How?

Solution 1:

Route Print on my local machine shows: 192.168.10.99 255.255.255.255 On-link 10.168.10.154 26

That is why, the On-link routes are accessible locally without any gateway, many times they are created when you connect via dial-up (to Avaya device maybe). You have to find out why this route is being created. Maybe it was just a left over or was added manually in the past as a persistent route, Try deleting the route, ping, then reboot and ping to see it was not created again somehow.

Solution 2:

It looks to me like you have an additional ip address assigned to your NIC.