Tax requirements on land sales for non resident foreigners

Sorry if this has already been covered.According to this article extract below all non resident land owners need to register for a FIRTPA with the IRS. My question is if a non resident foreigner buys and then sells a lot and the profit after expenses is only 5k or 10 k or under whatever the capital gains threshold is, would we still need to register with the IRS? So if CGT is only payable on anything over 20k for example could we just keep our deals/profits under that to avoid having to deal with the IRS?

‘Under FIRTPA (Foreign Investment in Real Property Tax Act), when a non-resident foreigner sells US real estate, a portion of the sale proceeds (usually 10%-15%) must be withheld by the buyer at closing and remitted to the IRS.’

Obviously we are aware property taxes will need to be paid to the county regardless. Any info would be great,we do not want to do anything ilegal we just want to know what legal loopholes are available.

Many thanks in advance