Does this line create a subshell?

[Robert E. Griffith]

Does this line create a subshell when 'foo' is a loadable builtin that 
produces output on stdout?

   local line; read -r line <(builtin foo)

Would that line be about the same in the amount of runtime work done 
(i.e. just as quick) as writing the builtin to set the value of a shell 
variable whose name is passed into it?

   local line; builtin foo "line"

--BobG