150F internal seems kind of high.
Both Ariane Daguin and her father recommend 115-120 and I’ve even seen recipes that call for chilling when the IT reaches 100F.
My technique comes from The Professional Charcuterie Series. All the terrine recipes I have tried from the series have been very successful although I have never tried the low temperatures you cite. At 150F followed by rapid cooling, the proteins in the liver have denatured, but the fat has not liquified. I would think that the difference in texture between these two techniques would be dramatic.