That interpretation makes sense.
On the other hand, the C-195/17 linked above seems to be of a different opinion.
In 3.56, it reiterates that airline strikes are extraordinary circumstances which could not have been avoided:
"56. On the other hand, recital 14 of Regulation No 261/2004 states that, as under the Montreal Convention, obligations on operating air carriers should be limited or excluded in cases where an event has been caused by extraordinary circumstances which could not have been avoided even if all reasonable measures had been taken. Such circumstances may, in particular, occur in cases of political instability, meteorological conditions incompatible with the operation of the flight concerned, security risks, unexpected flight safety shortcomings and strikes that affect the operation of an operating air carrier."

The ruling is specifically devoted to a wild-cat strike by employees under the guise of sick-leave. It is an extraordinary circumstance. My reading is that if the number is small, the extraordinary circumstance could have been avoided by the airline. If the number of absentees is high, it could not have been avoided by the airline.The ruling lets the courts interpret what is a high rate of absentees.

In the case of a legal strike, there is little doubt that the airline cannot avoid the consequences of this extraordinary circumstance. After careful reading (I am not a lawyer), I cannot see how this ruling could be used for a legal strike. It even reiterates in 3.56 that strikes are extraordinary circumstances thta cannot be avoided even if all reasonable measures had been take.

IMO Air France has been very generous in providing compensation, but it seems to me to be more a commercial gesture than required by EC261/2004.