The article you linked explains that the IRS has taken the position that these expenses are not deductible. The Revenue Rulings just "help" in determining when they aren't deductible. Congress intended for the forgiveness to be tax exempt. There is a section of the Internal Revenue Code that states that expenses are not deductible to the extent they are paid with tax exempt funds. The IRS took this section and applied it to PPP loan forgiveness and decided that these expenses are nondeductible.
If you have tax exempt forgiveness but the expenses paid with the loans are nondeductible, you have taxable forgiveness. Again, I'm not arguing that these loans should be forgiven tax-free for all - there are absolutely people who abused them, just look at some Sedgwick County Commissioners - but Congress clearly meant for these loans to be "free." Employers would not have retained workers with these loans when business was down if they knew they would be paying 40% of their wages in taxes. Congress didn't think things through with their bill, per usual, and the IRS overstepped.
They are idiots but it's not a loophole in the new relief. Dealing with these stupid PPP loans is part of my job.