"Is the article saying that sometimes low grade lymphomas can have no growth (in nodal size at least) for extended periods..."
Yes, that's what it claims.
"or it is saying that typically there would still be increased size after a year but rarely with low grade there isn’t"
Yes. More specifically, it is also purposefully excluding metastatic cancer from having zero growth in nodes.
I'd keep in mind that the article is from 2002, it cites a book from 1993 and a study from 1980, etc. The passage about the 1980 study says, "In one series of 628 patients undergoing nodal biopsy, benign or self-limited causes were found in 79 percent of patients younger than 30 years of age, versus 59 percent in patients 31 to 50 years of age and 39 percent in those older than 50 years."
Much more recent data says that the incidence of cancer in people who see a doctor because of unexplained lymphadenopathy is around 2%, among all ages combined. I haven't seen that broken down by age, but the % would increase according to age.
"I’ve read before that low grade lymphomas are common in young adults but then also read that low grade cancer s in young people are incredibly rare at the same time so I’m a bit confused by that."
They probably meant that it is rare, but when it happens it is likley to be low rather than high grade.
"is that implying that low grades in general wouldn’t see growth in a year?"
Nope, it would be very rare to see no growth in a year without any treatment.
"in person he even said if I go two years with no growth to him it’s basically as solid as an excision to him (regarding cancer at least)"
Yes, so true - but there is even a twist: sometimes even post-excision pathology can't be sure. The report might say 'suspicious". That'd also be very rare.
A biopsy is really only sure if it definitely finds a cancer, not if it doesn't find one.