Confusion about DTLs/DTAs

Can someone please clarify when a DTL/DTA is created? I've read way too many contradictory posts now...

According to Wall Street Prep: https://www.wallstreetprep.com/knowledge/financia…
As the example above illustrates, the DTL is created to reflect that due to different book vs. tax depreciation rates, there is a temporary timing difference leading to a lower payment to the IRS than reported for book purposes.

Also from Investopedia: https://www.investopedia.com/ask/answers/052915/w…
Consider a company with a 30% tax rate that depreciates an asset worth $10,000 placed in service in 2015 over 10 years. In the second year of the asset's service, the company records $1,000 of straight-line depreciation in its financial books and $1,800 MACRS depreciation in its tax books. The difference of $800 represents a temporary difference, which the company expects to eliminate by year 10 and pay higher taxes after that. The company records $240 ($800 × 30%) as a deferred tax liability on its financial statements.

So to my understanding when book taxes > cash taxes then the DTL goes up.

If that's the case, how come in a M&A deal structured as a stock purchase, when we write up assets on book accounting without an equivalent step-up on tax basis, we have an initial DTL created? If we write up assets without tax basis step-up then the D&A expense is higher for book vs. cash accounting, and therefore book taxes cash taxes implies DTL up. How come when we adjust balance sheet proforma for M&A/LBO transaction we have DTL going up with book