What Plain Text is
Plain text here means columns lined up with spaces, the way a command line tool prints a table.
Terminal output, log files, fixed-width exports from older systems.
What AsciiDoc is
AsciiDoc tables are delimited by |=== and take a cols attribute describing the columns.
Antora documentation sites, and technical writing teams that outgrew Markdown.
What changes when you convert Plain Text to AsciiDoc
Two shapes are handled. If the same character positions are blank on every line, those gutters are treated as column boundaries, so values containing single spaces stay intact. Otherwise the lines are split on runs of whitespace.
The header option is set so the first row renders as a header row rather than data.
What carries over from Plain Text to AsciiDoc
AsciiDoc can express everything plain text holds about a table, so this conversion is about shape rather than loss.
AsciiDoc marks its header cells differently from its data cells, so the first row is written with that marker.
The identifier 007 comes out of the AsciiDoc as 007. Reading it as a number would have made it 7, and an id that changes value is worse than one that stays text.
The role "Analyst, data" survives with its comma, in one cell rather than split across two. That is the first thing to check in any converted table, and the usual place a AsciiDoc file goes wrong.
The quotes around Jonah "Jo" Pryce are left as a plain quote character in the AsciiDoc.