BUG: string series to numpy array conversion

[deepspacesparkle]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

df = pd.DataFrame({'a':["1","2","3"]}, dtype="string")

type(df['a'].values)
type(df['a'].unique())

Issue Description

I am getting pandas.core.arrays.string_.StringArray when converting pandas string series to NumPy array with unique or values methods. Could be associated with #46366

Expected Behavior

pandas.values and pandas.unique returns np.ndarray

Installed Versions

pandas: 1.3.5, numpy: 1.21.3

[SeanRBurton]

StringArray derives from ExtensionArray which is documented as a possible return type of unique. I would say this is more a case of insufficient documentation than a bug.