[Python] as_index=False groupBy doesn't work with count

When I run groupby on a dataframe with as_index set to False, count seems to not work at all. For example,

import pandas as pd

word_list = ['a', 'b', 'c', 'a', 'c', 'c', 'b', 'a', 'c']

df = pd.DataFrame(word_list, columns=['word'])
as_counts = df.groupby('word', as_index=False).count()
print(as_counts)


word
0 a
1 b
2 c


If you try the same with .size() as in

as_counts = df.groupby('word', as_index=False).size()


it works as expected

word size
0 a 3
1 b 2
2 c 4


What difference between the two functions explains this difference in output?

This post is asking a different question entirely as, in this case, the frame is neither MultiIndex nor seeking to maintain non-unique indices. Equally, none of the answers in that post address the problem of this question.

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