API: pd.concat with len(keys) != len(values) does not raise; intentional?

[jbrockmendel]

import pandas as pd
ser = pd.Series(range(5))
sers = [ser + n for n in range(4)]
keys = ["A", "B", "C"]

>>> pd.concat(sers, keys=keys, axis=1)
   A  B  C
0  0  1  2
1  1  2  3
2  2  3  4
3  3  4  5
4  4  5  6

I expected the pd.concat below to raise. It kind of makes sense as a reindex or analogue to the DataFrame constructor, but seems more likely to me to be a footgun. In particular, I think the lack of raising may be hiding a bug in the groupby code.

Is not-raising an intentional decision? If so, thoughts on either deprecating or issuing a warning?