It seems to me that Rav Shach is learning the sugia on page 23 of bava kama in away that is similar to the Gra because he says in Nizkei Mamon 14 chapter halacha 15 that even though fire is liable because of his arrows still it is not exactly like his arrows. He brings a proof from hidden things. For hidden things, one would be liable by actual damage by means of one’s arrows, but in the case of fire, one is not obligated when it is for things that are not customarily hidden inside a stack. So, Rav Shach does learn like the Gra at least in terms of the result that fire is not like his arrows for anything except the four types of damage. I have mentioned before that the Gra wrote that the way the Rif Rambam and semag learn the subject of page 23 is that R Yochanas holds differently than what we thought originally. At first, we thought he meant fire is because his arrows mean it is damage by one’s direct action. Now instead we think it is only like damage by mean of one’s property like his ox, and it is like fire only in term of four extra type of payment.