Did you notice how Oda is progressively increasing the power of Sanji's IJ?
In Wano, IJ was a blue flame with small sparks of plasma.
Then, at the beginning of Elbaf, IJ looked much more shimmering and the plasma sparks much thicker and larger.
Now against Killingham and Imu, Oda drew IJ to look so hot that Sanji's leg glows in a completely different star-like pattern than Oda drew it before.
I feel like Oda is rushing the development of Sanji's flames.