What deferred tax liability consequences do step-ups have in a stock deal, and why does that not reduce goodwill one-for-one?

In a stock deal, accounting fair-value step-ups often do not create a tax basis step-up. The difference between book basis and tax basis creates a deferred tax liability. Goodwill increases by the DTL because the buyer recognizes an additional liability assumed. The step-up does not reduce goodwill one-for-one because the DTL partially offsets the net identifiable asset increase.