Has any commentary explained why the Torah reading for fast days doesn't begin at a parsha?

Every public Torah reading, except for two, begins at a parsha (the start of a new "paragraph" as written in a Torah scroll.)

The two exceptions are:

• Vayechi which has a space of just one letter between the end of Vayigash and the start of Vayechi. Rash"i among others, explains why there is just one space rather than being a normal "parsha" space (possibly a setumah / closed parsha.)


• The public Torah reading for public fast days (except Yom Kippur and 9 Av morning) begins at Shemot 32:11 with the word "Vayechal".

Is there any commentary or rabbi, etc. that explains why Vayechal begins in the middle of a parsha, and why it is the only reading that does so?