It isn’t the same argument.
The claim was that Corbyn was unelectable; clearly given the fact that ten million plus people voted for him, twice, this is nonsense. He was more electable than any Labour leader since Blair.
Think this is a bit semantic. He was electable because he acquired so many votes, but he also inspired more votes to vote against him, which means he was - not elected.
If electable just means ‘getting more votes than previously’ that’s fine. But it misses out the key bit of being divisive to the point that it results in an engaged and motivated opposition.