Putting aside the possibility of rejection.
What do they get out of it for approving it before the election? If the only people that care are the companies and their shareholders, then I don't think the Government would want to allow vote slippage from the Coastal electorates they do hold, to occur, just to appease a couple of small cap companies. I don't think the industry cares, because their approvals have been pretty much the same, (and the corporate siege that the Joint Authority is imposing on BPH, MMR, BUY is probably a benefit to the competitors) the naysayers are happy there is no "approval", and I think the Liberals/Nationals would rather be seen as intentionally stalling/obstructionist than to give the opposition yet another reason to oppose them.
There is one scenario that might have a positive spin for pre-election approval, and that is for them to approve it as close to the election as possible (5 weeks before possibly when the parliament is dissolved [that would mean the decision would be a week or two after parliament dissolves due to NOPTA processing times + trading halt]). And the reason this might be a plausible scenario is because the Liberals might be giving Labor a political 'ticking time bomb' which will go off 2 years into the next term, for whoever that may be. Then whoever gets the next term has to navigate a "renewal" or "production license" which is 100x more important than an extension.
Putting your theory to the test: "approve before the election as the electorates affected by PEP-11 are already heavily pro-Labor, so they wouldn't have much to gain"
-MP's two party preferred swing adapted from Australian Electoral Commission (AEC) 2019 Federal election Results Map.
As we can see from this map adapted from the AEC 2019 above, if we just assume Warringah is "Coalition" for the sake of assuming Zali will lose her seat because the only reason she got elected was because "Abbott was blamed for destabilising the party since losing the prime ministership himself in the lead up to the 2016 election."
https://theconversation.com/abbotts-loss-in-warringah-shows-voters-rejecting-an-out-of-touch-candidate-and-a-nasty-style-of-politics-117379 and it had been held by the Liberals and their predecessors without interruption since its creation in 1922. Then we can see that there are 6 Coalition vs 5 Labor coastal seats (assuming Craig Kelly (now an independent) is also replaced by the next Liberal MP). So I don't agree with the premise that it is "already heavily pro-Labor".
If you say that "well I meant the seats directly adjacent to the permit area" then yes that would then be true. But we know from the political discussions so far that the politicians themselves don't believe that only the seats directly adjacent to PEP-11 are affected, for example both Matt Thistlethwaite and Dave Sharma were at the Surfrider STOP PEP-11 town halls.
The bottom line is, Liberals have more to lose by approving it than just sitting on their hands. If it gets delayed or approved, I don't think Labor's voters would change, but fence sitting Liberal leaning voters may.
(20min delay)