Through does not have hold attribute?

Possibly Related to Unexpected behavior of KeyTake.

Consider the following example, where I input #11 (last) is the misbehaving one. Am I missing something or do you agree there is a bug?

In[1]:= assoc = <|1 -> "x", 2 -> "y"|> Out[1]= <|1 -> "x", 2 -> "y"|> In[2]:= KeyTake[{1}][assoc] Out[2]= <|1 -> "x"|> In[3]:= <|2 -> #[2]|> &[assoc] Out[3]= <|2 -> "y"|> In[4]:= f1 = KeyTake[{1}]; In[5]:= f2 = <|2 -> #[2]|> &; In[6]:= f3[x_] := KeyTake[x, {1}]; In[7]:= f4[x_] := KeyTake[{1}][x]; In[8]:= Join[f1[assoc], f2[assoc]] Out[8]= <|1 -> "x", 2 -> "y"|> In[9]:= Through[Join[f4, f2][assoc]] Out[9]= <|1 -> "x", 2 -> "y"|> In[10]:= Through[Join[f3, f2][assoc]] Out[10]= <|1 -> "x", 2 -> "y"|> In[11]:= Through[Join[f1, f2][assoc]] During evaluation of In[11]:= Join::heads: Heads KeyTake and Function at positions 1 and 2 are expected to be the same. Out[11]= <|1 -> "x", 2 -> "y"|> 

Inexplicably we still get the correct result. Why is that?

I think the error is caused by the fact that Through Does not have Hold* Attribute, which I find to be strange given what it is supposed to do.

In[12]:= Attributes[Through] Out[12]= {Protected} 

An alternative implementation that does hold arguments seems to work fine, though I haven't tested it too much and it may have other bugs:

ClearAll[through] SetAttributes[through, HoldAll] through[head_[args__][arg__]] := Apply[head, Map[#[arg] &, {args}]]; In[31]:= through[Join[f1, f2][assoc]] Out[31]= <|1 -> "x", 2 -> "y"|> ```