This is significant as this is the first border crossing with Israel that is in the hands of the Syrian rebels. Not only that, but if reports of Nusra involvement are true, this would put al-Qaeda forces at a much closer distance to Israeli forces in the Golan. But this might also cause some problems for Nusra. Israel, as they have shown time and time again with Palestinian militants or the Lebanese-Hezbollah, they are quite proactive at eliminating perceived threats against the Jewish state. If Nusra were to come out and publicly say that they are in control of the crossing, it might prompt Israeli action. This may be why the SRF seems to be the only group disseminating these videos of controlling the crossing. And, of course, this could be too early to tell and Nusra is waiting for some video to be done to announce this victory.
One thing is for sure, though, is that Israel will not take this lightly. They will most certainly keep a keen eye on this and will more than likely strike whenever they feel threatened by Nusra being so close. As the Washington Institute noted back in January: "Concerned about the possible drift of al-Qaeda affiliates to areas adjacent to the Golan Heights border, Israel finds itself obliged to increase its assistance to local rebel militias in southern Syria." One thing the now-outdated article says is that by Nusra pushing further into Israel via the Golan would give al-Qaeda a front with Israel. However, it seems unlikely that Nusra would so given that they are still heavily invested in battling the Assad regime, have been consolidating their power in Idlib and other governorates, and are still very committed to fighting ISIS. But, Nusra needn't push too far to entice an Israeli response. Having al-Qaeda that close to them is a big enough threat for Israel. Like I said above, this is why Nusra seems to be letting others take responsibility for this.
Below are some embedded tweets for further confirmation:
Here is another video showing the SRF at the border crossing:
Finally, here is a Facebook post from the SRF page which states that they have "liberated the border between occupied Golan and Quneitra".
I took out some dead twitter links and inserted a picture with the one dead link still left.