Is there any explanation on why this character has 崇 as a component?

The dictionary, Giúp Đọc, just explains the structure: "thủ" = 手 and the phonetic, "sùng" 崇. The final, 'ung' of 崇 is an exact match, so I guess the question is about the initial "s-". There are certainly many cases where the phonetic is not an exact match, but the use of "s-" here to represent a velar does seem to be an outlier. Possibly this is a borrowing from an older stage of Chinese that contained a velar (at least according to Baxter-Sagart reconstructions). For example, "sen" (lotus) is thought to be derived from 蓮, which they reconstruct as *k.[r]ˤe[n]. Similarly, the word river, "sông" is thought to be derived from an earlier Austroasiatic word similar to Mon "kruŋ". Perhaps in some circumstances, the velar was retained.

Seen in the PUA font of Surveying and Mapping of Jiangxi(江西) Province, U+EE9A.