"With your lower mash temp, you could extend your mash to 90 minutes to get a little more conversion. This can increase your OG versus a 60 minute mash. Not sure if you’re going for that or not."
A long rest at 148F causes beer to be thin and dry. FG should end up close to expected FG.
At 148F Beta is active and conversion occurs, but at 148F Beta doesn't last too long, it denatures. During conversion Beta converts glucose released by Alpha during saccharification into maltose and maltotriose which are complex types of sugar that yeast doesn't like as much as glucose. After Beta denatures, Alpha continues to release sweet tasting, nonfermenting sugar and glucose which yeast likes a lot, until denaturing. At 148F more glucose than sweet, nonfermenting sugar is released.
During primary fermentation yeast rips through glucose cranking out ABV and leaves sweet and complex sugar behind.
Assuming the malt contained Beta, which it doesn't need to contain to be called malt, the wort will contain maltose and maltotriose which yeast does nothing with until secondary fermentation and aging. During secondary fermentation yeast absorbs maltose through the cell wall and an enzyme within yeast converts maltose back into the sugar it came from, glucose. The glucose is expelled through the cell wall and it becomes yeast fuel. Gravity reduces closer to expected FG. During aging the same thing happens to maltotriose and natural carbonation occurs. FG is hit.
When beer is primed and complex sugar is in the mix, yeast goes after the priming sugar, and then, it goes after complex sugar. Over carbonation, gushers, bottle bombs can happen.