A criteria for Emoji property assignment?

[Rostislav via Unicode]

I wonder what reason lies behind Unicode Consortium’s declaring some decorative characters as emojis while leaving some other in the state of regular characters.

For example:

1. Four arrows (←↑→↓, 2190…2193) are not emojis, while the four diagonal arrows in the same Unicode block (↖↗↘↙, 2196…2199) are emojis.

2. 23F9 (⏹) and 23FA (⏺) are emojis, but the next two characters 23FB (⏻) and 23FC (⏼) aren’t.

3. In the Geometric Shapes block, only two characters (25AA ▪ and 25AB ▫) are considered emojis, while other 94 aren’t. While did just these two little squares deserve the honor of bearing Emoji property, in contrast to all other geometric shapes?

4. In the Miscellaneous Symbols block, there is a suspicion that the characters were appointed emojis randomly. Two snowmen (2603 ☃ and 26C4 ⛄) are emojis, but the third one (26C7 ⛇) is not; the up-pointing finger (261D ☝) is an emoji, the down-pointing one (261F ☟) is not: a cloud without rain (2601 ☁) and with rain (26C8 ⛈) are emojis, but a rain without cloud (26C6 ⛆) isn’t. Of the characters originated from the single source (namely ARIB, L2/07-391), some became emojis, some not—without any apparent logic.

5. More strange, on the first page of Miscellaneous Symbols and Pictographs (1F300…1F3FF) almost all characters are emojis, except for 10 that are gnawed out inexplicably (e.g. 1F395 �� and 1F3F2 ��). A similar situation is in the Supplemental Symbols and Pictographs block, where a rifle (1F946 ��) is excluded from emojis, though almost all other characters have Emoji property.

On the whole, almost every Unicode emoji raises a question, why some or many other similar characters aren’t emojis like this one; and lots of non-emojis also rise questions why they aren’t. The assignment of Emoji property to characters seems to be inconsistent, arbitrary and unexplainable,

Or is there an unified explanation of criteria for Emoji property assignment?

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