You are years behind the information curve. We've known for decades that Mao had no intention of sending combat units into Vietnam, largely because Red Chinese forces were badly mauled in the Korean War. Mao was willing to provide massive aid to North Vietnam and to put some logistics troops into the northern part of North Vietnam, but that was as far as he was willing to go.
The boogey man of Chinese intervention was used by defeatist liberals to talk LBJ out of attacking the NVA/VC sanctuaries in Cambodia and Laos, to talk him out of making full use of our air power against North Vietnam, and to talk him out of mining Haiphong Harbor. When Nixon unleashed two massive bombing campaigns against North Vietnam and mined Haiphong Harbor (and other harbors) in 1972, the Chinese did not intervene, despite urgent pleas from Hanoi that they do so.