I'm not sure. I don't actually know that much amount APL history. I've really only used it for a few years. If you want a lot more information about that, I recommend you join the GNU APL mailing list, as some of the members there know a lot about the history: https://lists.gnu.org/mailman/listinfo/bug-apl
As far as I know, Sharp APL was "old style" in the sense that it did not support nested arrays. Some people may like that style, but I have a hard time seeing that it is "better", since the nesed arrays are backward compatible with the non-nested style.
Note that you can also use the ⊂ and ⊃ functions to convert between nested and recursive arrays. For example, assuming you have an array of strings:
a ← 'here' 'are' 'some' 'strings'
⍝ a is now a single-dimensional array of 4 elements
⍴a
4
⍝ The ⊃ function converts the nested array into a two-dimensional array
⊃a
here
are
some
strings
⍝ The array is two-dimensional with 4 rows and 7 columns
⍴ ⊃a
4 7
As far as I know, Sharp APL was "old style" in the sense that it did not support nested arrays. Some people may like that style, but I have a hard time seeing that it is "better", since the nesed arrays are backward compatible with the non-nested style.
Note that you can also use the ⊂ and ⊃ functions to convert between nested and recursive arrays. For example, assuming you have an array of strings: