I first had Yoroi mobile and kept my ADA there + staked through the app. Got Daedalus for the desktop to set up for the next fund voting, and imported my balance via my phrase. Now I see my balance and stake pool in each. Is that just a function of ADA that you can access / move / manage your assets with multiple wallets?
Yes - this is like opening your email box with different mail client.
@laplasz analogy is correct.
The reason its correct is that your funds are not stored in you wallets, but rather they are stored on the Cardano blockchain, but can only be accessed (ie spent) by someone who has access to your secret key. Since both Daedalus and Yoroi have access to your secret key, and they are both accessing the same blockchain, both wallets should display the same amounts.