I am learning about American odds (moneyline odds) and point spreads. In Chapter 2 of Sports Betting for Dummies, I see:
When the point spread on a game gets further from zero, the two moneyline bets get further apart. For example, they might move from -150 (on the favorite) and +135 (on the underdog) to -160 and +145.
I don't understand the example. From my intuition, when the point spread increases, the American odds (moneyline) on the favorite should increase (e.g. from -150 to -140 [and not decrease from -150 to -160 as in the example]). I don't see why anyone would accept a decreased potential profit when the probability of winning is decreased.
To give an extreme illustration, suppose the point spread increases from 0 to 1 quadrillion. To the best of my knowledge, no sports team has ever gained a 1 quadrillion point lead over their opponent, so a bet on the favorite will likely never win if there is a point spread of 1 quadrillion. Therefore, the moneyline on the favorite should increase (e.g. from -150 to +100000000000...).
Furthermore, I don't see how the first sentence is true:
When the point spread on a game gets further from zero, the two moneyline bets get further apart.
From my intuition, if the point spread is increased to a level such that the bet on the favorite and the bet on the underdog have increasingly equal probability of winning, the two moneyline bets should get closer together (and not further apart). For example, if the point spread is x, and this x point spread results in bets on both sides getting a 50% probability of winning, their moneyline should be equal (e.g. -110 and -110). Therefore, when the point spread on a game gets further from zero, the two moneyline bets get closer together before moving further apart.
Am I wrong? If so, could you explain what I'm missing?