It looks like someone mistakenly analysed 蒙 as the simplified form of ⿱𤇾⿱一豕, analagous to 萦~縈 etc. Is the ⿱𤇾⿱一豕 form used in other sources? It would be prudent to see actual textual examples of this character before encoding it, especially as the evidence page also shows this form of 蒙 with 月, 氵, 虫, and 木 radicals which I suppose would be submitted for a future working set.

kMandarin měng

The only additional evidence I have on hand is from the Chinese-Vietnamese dictionary "Nhật Dụng Thường Đàm", p 50b. where the character appears in the name of a bird "mòng két" (common teal)



In modern printed form, the text is:

phù ê: là mòng két (nhất danh vịt nước) = "鳬鷖 is the common teal (another name is water duck)"