The video was about how we have insight on Viking Runic Language due to cross-referencing them with the way Muslim Vikings used the language, but at the beginning it claimed what I just asked in the title. If this is too specific, how, if at all, did cheese come to have a role in the 11th or 12th century Iberia?
This claim seems to originate from the Ibero-Islamic legal scholar ʿAbd al-Malik ibn Habīb (790-893). In his Kitab al-Tarikh (Book of History), Ibn Habib recorded:
It is not harmful to eat the cheese of the Rūm and so forth of the enemy among the Peoples of the Book. But one must not eat the cheese of the Majūs'.
This ruling is preserved without further context, but we can infer a few things directly from it. First, it's not just about cheese. It's about 'cheese ... and so forth', which in the second half of the ruling is more simply stated as just 'cheese', but the implication seems to be that the ruling is about processed food in general.
Second, it's not about the viking Norse. It's about the Rūm and the Majūs'. The Rūm, or Romans, were the Byzantines, and the most important thing about them here is that they were a People of the Book (i.e. one of the Abrahamic religions). The Majūs', however, are implicitly not People of the Book. But does this make them vikings?
Not necessarily. There were viking raids on Spain. We have reliable records for one in 844 along the Atlantic coast, one in 859 that continued through the Straits of Gibraltar into the western Mediterranean, and some sporadic raiding in the 1100s. These last raids seem to have been mostly quick raiding stops by crusaders from Scandinavia or Iceland en route to the Holy Land, and they fall outside the Viking Age proper (ca. 750-1050), so it's up to you if you want to count them.
There's also some archaeological evidence for viking activity in the south: a few Norse artifacts that have been found in Spain, a small fort that looks like the kind of temporary beach protection vikings would construct where they landed, and the remains of an early medieval mouse with Scandinavian ancestry found far off the Atlantic coast on Madeira.
So there were Norse raiders in Iberia in the 800s, when Ibn Habib was writing, and they were in fact called Majūs' in the written sources. But this was also a more generic term used to refer to any kind of pagan. It's related to the words Magi and magic, and in the 900s, the Arabic geographer Ibn Ḥawqal listed the Majūs' as a religious category that could include people of ethnicities such as the Turks, Pechenegs, Saqāliba (possibly Slavs), and Bulgars. So although all vikings were Majūs', not all Majūs' were vikings—we have no reason to assume that Ibn Habib's ruling was specifically about viking visitors from the north.
In sum, the video you watched is based on historical evidence, but it's got some fundamental misinterpretations of the sources. There were viking raids on Iberia in the 800s, at which time there were also rulings that Muslims shouldn't eat foods processed by pagans. It's not clear whether these two circumstances were related or whether they were purely coincidental. There were also Norse raiders in Iberia in the 1100s, but by this time they were a People of the Book, so if they stayed long enough to make cheese, it would have been licit for an Iberian Muslim to eat it.
The indispensable source for any questions about vikings in Iberia is:
Could you link the video? I'd be interested in seeing what sources they use.