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

["積丹尼 Dan Jacobson" <jidanni@jidanni.org>]

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".