In other words, these two things would have been equivalent in Python:
a ← 23
a = 23
I do not consider these two things conceptually equivalent. In Python the identifier ('a' in this case) is just label to the value, I can imagine "let 'a' point to the value of 23 now" and write it this way: "a --> 23", but "a <-- 23" does give an impression that 23 points to, or is somehow fed into, 'a'. This may give false expectations to those who are coming to Python from another language and might expect the "l-value" behavior in Python.
Second point, I can write := in two keystrokes, but I do not have a dedicated key for the arrow on my keyboard. Should '<--' also be an acceptable syntax?