bug#49003: completion-list: vertical vs. horizontal

[積丹尼 Dan Jacobson]

Here we are in the Completion List buffer.

   Click on a completion to select it.
   In this buffer, type RET to select the completion near point.

   Possible completions are:
   MIME::Base64(3perl)  MIME::Body(3pm)         MIME::Charset(3pm)      
MIME::Decoder(3pm)      MIME::Decoder::Base64(3pm)      
MIME::Decoder::BinHex(3pm)      MIME::Decoder::Binary(3pm)
   MIME::Decoder::Gzip64(3pm)   MIME::Decoder::NBit(3pm)        
MIME::Decoder::QuotedPrint(3pm)         MIME::Decoder::UU(3pm)  
MIME::Entity(3pm)       MIME::Field::ConTraEnc(3pm)     
MIME::Field::ContDisp(3pm)
   MIME::Field::ContType(3pm)   MIME::Field::ParamVal(3pm)      MIME::Head(3pm) 
        MIME::Parser(3pm)       MIME::Parser::Filer(3pm)        
MIME::Parser::Reader(3pm)       MIME::Parser::Results(3pm)
   MIME::QuotedPrint(3perl)     MIME::Tools(3pm)        MIME::Type(3pm)         
MIME::Types(3pm)        MIME::WordDecoder(3pm)  MIME::Words(3pm)

Currently they are listed
1       2       3       4
5       6       7       8

I wish they were listed
1       3       5       7
2       4       6       8

because it is easier on my eyes / brain.

In fact that is how C-x C-d (list-directory) works.

Alas there is no completion-list-bla variable to set, nor no mention on (info 
"(emacs) Completion").
emacs-version "27.1".