My impression is that gambling losses have “always” (at least in recent time before the new tax law) been taken as itemized deductions (limited to the amount of the winnings). This meant that you could only benefit from the losses if you itemized. I am not aware of any case where you could offset losses against winnings if you used the setandard deduction.
“After applying the losses-cannot-exceed-winnings limitation, the allowable gambling loss deduction for a person who is not a professional gambler is claimed on Line 28 of Schedule A (Itemized Deductions). If you don’t itemize, you get no write-off“
seems to me that even in the old days declaring a “net”gambling win (offset w/ loss) is like declaring a “net capital gain” (offset gross proceeds with basis) and omitting basis.
In the latter the math is correct but IRS will see that the gross proceeds do not agree w/ the 1099B and will come after you for more. Still you can show the correct reporting w/ basis declared and gross proceeds and prove you are correct.
In the base of gambling, IRS again will see that your reported winnings do not match the W-2G and discover that you are not reporting losses properly.