I noticed that there is a variant of the 之繞 radical ⻌ which occurs in some words but not others. The variant is 辶 (with an extra stroke). It appears in words like 逢う and 槌.

It turns out that Non-Joyo kanji which use the 之繞 radical are written with the variant 辶 while Joyo kanji use the more common ⻌ - "常用漢字以外は「辶」を用いる" (See details here).
Are there any other radicals which have variants that are differentiated by Joyo vs Non-Joyo?