can my phone tell me an exact location of my apple watch

It depends on certain factors. Generally, your iPhone can give you a very close proximity location of your Apple Watch - IF - It is powered on, connected to a network and Find My has been enabled. In terms of location, its connection to the network will determine how accurately it can pinpoint it's location.

In general I agree with lobsterghost1, the FindMy app will give you a pretty close location for your devices. However, I disagree about network connection governing the accuracy and precision of the fix. The Network connection is only relevant for allowing each device to communicate and share location to FindMy - if no connection then no location, or old and stale location which might no longer be correct.

Whether the determined location in FindMy is "exact" depends mainly on two things,

(a) The quality of GPS fix each device can achieve. Like any GPS fix this will depend on the local environment, the number of satellites visible, and obstructed signals. Outside with a clear view of the sky your devices might get as good as 2-3 metres accuracy. Inside a building this might often degrade to accuracy like 10-20m circle or even worse. In some cases a building structure could even block view of all the satellites so there is no position fix (think basement, but some types of solar reflecting glass are metal coated may and block signals).

(b) Your opinion of what counts as "exact". A basic GPS may be accurate to within a 50 metre circle. Almost any recent GPS will be within 10m circle for 95% of its fixes. A survey grade GPS may be accurate to better than 1m (possibly as good as 0.1m) but you would not expect that from a consumer grade GPS in a smartphone.

I think you gave a better explanation and perhaps, my comment about the network should have included the GPS part you went into more detail about. For the most part, unless its connected to a network, the GPS location won't be known, so that is basically what I was trying to say.