Deductions & credits

Read Pub 551 page 10 and agree with TomD8....but the IRS makes no sense....what's the difference if the father and son buy property held as jtwros and father pays 90% at closing and son pays 10% at closing ****OR**** father gives son cash right before closing and father and son each pay 50% at closing? Results should be the same but they're not according to the IRS.