Some small but IMO important DL details:
As I'm sure everyone knows, grounded DL's hop distance can be notably influenced by the pushing the control stick in the direction you're moving, so you can hold forwards (the direction Corrin is facing during the beginning of the move) to get maximum hop distance or don't move the stick forwards at all to get minimum distance (as a result,the shortest distance is equivalent to jumping in place, to do this essentially flick the stick for the S-B input and then immediately let go, or immediately move the stick in the direction opposite that which Corrin is facing).
One thing to note is that if you tilt the stick in the direction Corrin is facing in order to drift forwards, subsequently holding the opposite direction after Corrin has moved forwards will not move Corrin backwards, it will simply stop her forwards momentum and Corrin will begin to fall straight down at the spot in the air that she has reached during the forward hop.
Once you stop your forwards momentum by holding backwards, Corrin can then immediately begin drifting forwards again if you simply hold forwards, so you can weave through the air and mix up spacing, although this mix-up capability really only becomes significant when Corrin is performing grounded DL and then traveling to a lower vertical postiion, because if Corrin starts and ends her DL on say, the base of FD, and is landing at the same height that she began, there won't be very much time for such momentum shifting to make a significant impact (Please note: I'm referring only to momentum shifting forwards and backwards repeatedly, the momentum stops that shorten Corrin's initial hop distance are still valuable when performing grounded DL on a static height platform)
What's important about this hop is that it allows Corrin an easier way to grab ledge for trump attempts than Short Hops (since the DL hop is shorter, the timing doesn't need to be quite as precise as for a SH where you have extraneous air-time as you rise to SH height), the inconsistent run-off-stage-immediately-hold-backwards and standing right at the ledge and barely tilting the stick to fall into the ledge, and this is made even easier by the fact that you can influence the forwards/backwards distance of the hop by tilting forwards or backwards.
And because Corrin's Bair is amazing, this makes ledge trump Bair even easier, and I know we all like it when we can do more Bairs.
Another thing is that, as you may all have noticed, when Corrin does a grounded DL, after the actual hand-lance stab, if Corrin doesn't pin the ground, she is lifted up slightly (not a huge amount but an amount that is noticeable). The area where I think this slight difference may be significant would be with DL edgeguarding. Aerial DL has a much less significant stall when Corrin performs the lance stab than grounded DL.
So, if Corrin is choosing to go deep for a DL edgeguard, performing a grounded DL on the ledge and then just drifting offstage will allow Corrin to achieve a depth almost as far as simply falling with aerial DL (by the time the grounded DL hop animation ends, at which point Corrin CANNOT aerial DL afterwards). So, I feel like having this "extra boost" on DL will give Corrin a little more of a space buffer for when she needs to come back to the stage so that the frame window for being able to successfully make it back to the ledge isn't as tight since Corrin can double jump while she is rising from the grounded DL stab animation.
Another important thing to note about grounded DL offstage is that the stab remains an active option for as long as Corrin's "Dragon Mask" remains visible (I know it isn't a mask but stay with me), which is a deceptively long time since Corrin actually relaxes her lance arm before the Dragon Mask disappears.