Why would torching increase depletion?  Can oil and gas burn away while thousands of feet underground?
Saddam's troops blew the wellheads on lots (tens to hundreds) of wells in Burgan field.  It allowed them to flow unconstrainted at very high rates for months.  Some of them probably "coned" water in from below the oil reservoir.  This has a damaging effect on the reservoir.  Moreover, lots of reservoir pressure was lost, and lots of barrels (?volume?) ended up on the ground or were burned up.
Re: "coned" water in from below the oil reservoir

Could you explain that further? As regards lots of pressure being lost, that seems straightforward and no doubt accelerated declining flow rates as I talk about here. But it seems hard to believe that a truly significant volume was lost from the sabotage.
It has been estimated that Kuwait lost 2 billion barrels of oil due to the invasion (ASPO amongst other sources).
A picture is worth a thousand words. Perhaps I stand corrected vis-a-vis how much lost oil there was from Burgan back in 1991. I will say that as far as depletion goes regarding the peak, above the ground geopolitical factors (that led to this burn-off fire) count equally with geological considerations.