Scholars are mostly still okay using the term Reconquista or little-r reconquista for a couple of reasons. First, the map of Iberia did eventually shift from predominantly Islamic with a bit of Christian territory in the north to zealously Latin Christian, if we are using those lovely textbook color-coded political maps. Second, the papacy did attempt to make the Christian kingdoms' advance a sort of 'crusade in the West', offering soldiers the same indulgence (time off purgatory) for participation in Iberians wars as in the Near East and striving to redirect western French and Spanish soldiers from Jerusalem to Iberia.

But as Robin Vose has remarked, "reconquista" is somewhat of an anachronism, more convenient than historically accurate. The political situation in Iberia, especially during the fitna (era of the taifa kingdoms), and the peninsula's pattern of settlement make the situation on the ground much messier.

The taifas emerge as rivals out of the breakdown of the Cordoba caliphate, bickering/warring with each other as they jockeyed for power. Simply in terms of territorial possession, why wouldn't a Muslim king choose to ally with a Christian lord against a Muslim king who threatened his territory more immediately than the Christian? He might even gain some land in the process! The "reconquista" was not unidirectional--in fact, control of land along the frontier flowed back and forth quite a bit, although the net result was gain for various Christian lords.

The second thing to keep in mind is the spare settlement of the Iberian interior. Most of the "Christian"-"Muslim" frontier was actually unoccupied land or pastoral grazing--the colored blobs on a political map don't necessarily represent day-to-day power or even residence. When Christian lords conquered new territory, for example, they had to work really hard (i.e. pay people) to live there. In fact, Christian Iberia is one of the very few places in Latin Europe were Jews were allowed to own land for a period of time, since the new lords wanted basically any farmers they could get.

The taifa kingdoms, ultimately, would lose land but as a whole not fall to the Christians but to other Muslims! First the Almoravid and then the Almohad dynasties, who were more vehemently Muslim in the sense that they mandated stricter observance for Muslims (and in the case of the Almohads, occasionally massacred non-Muslims). Even in the Almohad army, however, we know there were a significant number of Christian mercenaries.

When you think about the reconquista as more a "net effect" that the papacy attempted to shape, but driven forward by individuals concerned most of all with their own power and authority, the complexity of the situation far beyond simply "Christian versus Muslim" pops into place.