They are still limited to 0.1s (100ms) for practicality. A bunch of games process new frames every ~30ms, which means our timers could be pretty inaccurate if we went below that. For example if you had a 20ms timer, it might work on a game that ticks every 10ms - but on a 30ms game it could wait 50ms before firing again.
Instead, we guarantee that a timer will fire within 100ms of accuracy. If you specify something more precise, like ".10289381" (which is allowed, since it's a float), that 2.89381ms won't do you any good.
Basically if you need finer grained control, you should (carefully) use OnGameFrame.
A good thing to read when thinking about timers, btw, is here: https://blogs.msdn.microsoft.com/old...02-00/?p=34333