Bruce is so caught up in his grief that he… misses Jason coming home.
Jason, fresh out of his grave and confused (and traumatized) as all hell is just wondering where the hell Alfred is (“I gave him a lengthy vacation, Jaylad.” “And he agreed!?!?!?”) and why Bruce is acting like everything Jason says and does is some kind of tear jerker and good gods, B, are you trying to die you can’t just drop down in the middle of a gun fight with no plan Jesus Christ and why haven’t you eaten the spaghetti I made you dad!?!
Bruce is just happy his mind is kind enough to create such a vivid hallucination of his dead son.