LyLo doesn't mean Town barely holds majority. It means if a non-Mafia is lynched, the Town doesn't win (i.e. ties or loses).
Let's say for example we have five players and two Mafia:
Anne - Vanilla Mafia
Bob - Vanilla Mafia
Charles - Doctor (can protect self)
Dick - Serial Killer
Earnie - Vanilla Townie
By your definition, this is LyLo.
However, Earnie can be lynched, and Bob and Dick are killed at Night, leaving Anne and Charles. Thus, a Mafia-Townie tie.
Earnie can be lynched, and Bob is killed at Night, with Dick being protected by Charles. This leaves Anne, Charles, and Dick. If Anne is lynched, it is a tie between the Town and Dick. If Charles is lynched, it is a tie between the Mafia and Dick. If Dick is lynched, the Mafia win.
Now imagine four players with two Mafia and two Serial Killers. xD