I think as Poe and Rey are talking we see several shots of either closeups or tight medium shots. So there’s plenty of time for Finn to walk up. I think it’s better this way than lightspeed skipping dialogue that doesn’t make sense if the TIEs don’t follow them into hyperspace. The only other way is to leave the scene untouched and to assume the term refers to jumping to lightspeed either through the ice or without calculations.
The horses arriving is a little abrupt but has to be that way to remove the compass.
I don’t think assuming lightspeed skipping, as referring to jumping through an ice wall without calculation, is a difficult logical jump to make. It would fit in with the rest of the technological babble that is commonplace in science fiction (including Star Wars.) We wouldn’t need an explanation of lightspeed skipping since we saw them do something that we hadn’t seen before, specifically lightspeed ramming through a wall and surviving. This alone would be considered lightspeed skipping in the context of this edit.
My issue with Finn walking up is that we can clearly see in the shot before he arrives that he is not there. It is not as if the shot where he is there he is just walking up, but he goes from not there to standing there as if he had been there this whole time without introducing himself. Rey would want to see him since we know from TFA and TLJ that their relationship is important to both of them. For Finn to return from a mission and Rey not acknowledge him at all doesn’t work for me.
With the horses, I get it, it is unfortunate though. I do think rearranging just two shots could make it flow better. I’m at the mechanic right now but I’ll try to explain my thought.
We see Rey looking over the Death Star wreckage after the Sith Whispers
We then see that one 2-second shot of the horse close-up coming over the hill
We then hear Poe say his line and pull up his blaster
We then see the shot of Poe’s blaster up with Janna coming down the hill
We would have to remove the 2-second shot from this point to fit continuity,
The scene then continues with no additional cuts.
To make this easier, perhaps removing Rey looking over the wreckage with the 2-second horse shot would allow for little audio adjustment.