Regarding
⦻ U+29BB CIRCLE WITH SUPERIMPOSED X,
there also should be a
SQUARE WITH SUPERIMPOSED X
as seen in map legends representing electrical towers.
Yes there are many Unicodes with X's in boxes,
$ unicode --max 0 --brief -r BOX.*X
☒ U+2612 BALLOT BOX WITH X
⮽ U+2BBD BALLOT BOX WITH LIGHT X
🗵 U+1F5F5 BALLOT BOX WITH SCRIPT X
🗷 U+1F5F7 BALLOT BOX WITH BOLD SCRIPT X
(and plenty others)
Regarding ⦻ U+29BB CIRCLE WITH SUPERIMPOSED X, there also should be a SQUARE WITH SUPERIMPOSED X as seen in map legends representing electrical towers. Yes there are many Unicodes with X's in boxes,
but none where the X exceeds the square!