Where an entry is drawn and what it says about itself.
properties and tooltip are User-Timing-only fields and this type cannot
say so. They reach DevTools through a performance.measure detail payload;
console.timeStamp(label, start, end, track, group, color) is the entire
signature and has no channel for them. A sink emitting through timeStamp
drops them rather than failing, because the alternative is a call site that
has to know which level the host is running at.
The pairs are [string, string] because that is what the panel renders, and
the conversion happens at the call site — ['patches', String(built)]. That
conversion is the reason properties never appears on a per-frame entry:
formatting a number allocates a string sixty times a second to fill a table
the cheap path discards anyway.