There are recipes where you would add less liquid and cook it for a shorter time. This is OK, but keep in mind that the resulting flavor will always be more bland.  The glossy, jammy, buttery texture of ube halaya comes from the cooking process. As the sugar, fat, and starch in the ingredients break down and mix together, they form a wonderfully creamy and glossy spread. All the flavors in the ingredients intensify during this cooking process, so it ideally shouldn’t be skipped or shortened.  This cooking technique is not unique to ube halaya. There are so many desserts in South Asian and South East Asian cooking that employ this technique. It results in a delightful melt-in-your-mouth, rich texture. And it's absolutely worth it!