This boils down to the question "What is a radical?"
In the loose sense, it's any part of a kanji, which occurs in a number of characters.
In some stricter sense, it's one of the 214 kanji radicals that have been used to index kanji characters ever since they appeared in the 1615 Zihui 1716 Kangxi Dictionary dictionaries.
For searching by applying a filter, having more radicals means more options to narrow down the characters to find the one you are looking for.
The radicals in the latter, stricter sense have a Japanese name. In general, the others don't.
Whether you consider a part of a kanji a radical or not, you can often describe parts either in terms of other kanji or in terms of katakana characters. This is because katakana characters are derived from kanji in the sense that they are precisely only a small characteristic part of a full character. Notably, ソ derives from the two dots on 曽. So any such dots can be said to "be" ソ.
For example, the 偕成社 6th year 漢字練習ノート says for 呼ぶ
くちへんに ノ ソ よこ一で たてまげはねる
Most if not all occurrences of the ソ "radical" are derived from the 八 radical (which is a radical in the strict sense), so 曽 itself has 曾 as traditional variant. In this sense ソ "is" also 八.