For the record, none of it had to do with Garrett's controversial propensity for going on Instagram and liking alt-right and homophobic memes, as well as jokes mocking Parkland school shooting survivors, posted by other Instagram users (for which he later apologized).
After being cooped up with Garrett for weeks while waiting for the finale to air, Becca has developed a problem with Garrett's snoring and messy habits.
"He snores so dang loud, and he likes to call it purring," Becca shared with Kimmel, before revealing her real pet peeve.
"He does this thing… where he loves paper towels, but he leaves them all around the house," Becca explained, getting more and more animated, while Garrett laughed awkwardly. "So everywhere I go it's like a crumpled paper towel here, and crumpled paper towel there. So I've started [sending] him videos all day long."
As for the tiny things Becca does that gets under Garrett's skin, the Reno, Nevada, native said he couldn't think of a single thing.
"Nope, nothing irks me," he said, showing off his diplomatic side.
He was similarly diplomatic when he took to a new Instagram account -- after deleting the account he used to like posts claiming Parkland student David Hogg is a crisis actor and memes mocking the transgender community -- to apologize for liking those posts.
"I am sorry to those who I offended, and I also take full responsibility for my 'likes' on Instagram that were hurtful and offensive. garrett_yrigs12 was my former Instagram handle and I decided to take it down and start fresh because I have learned an extremely valuable lesson and am taking steps to grow, become more educated, and be a better version of myself," Garrett wrote. "I am not perfect, and I will never be anywhere close, but now I will always be more informed and aware of what I am liking and supporting, not just on Instagram, but in life."
Becca, who has staunchly defended her new man throughout the season, was clearly satisfied by his apology, having connected with him throughout the season after she "just felt that Instant spark with him" the first time they spent time together.
While they've put the controversy behind them, Becca and Garrett said they are already working on the next challenge they're going to face: whether or not she is going to take his difficult-to-pronounce name.
"We've talked about maybe hyphenating it, but that's Kufrin-Yrigoyen, and I don't think our kids are going to be able to pronounce that," Becca admitted.
"You're gonna have to have really smart kids," Kimmel quipped.
Even Garrett admitted that he felt bad for the runner-up, and said he could see himself being brought to tears if he'd been in a similar situation.
"I mean, yeah, I put myself in his shoes," Garrett said, expressing empathy for Blake.
Becca, who said she's only seen bits and pieces of the finale, also sympathized with his crying fit.
"I've shed my fair share of tears," Becca said, adding that she "never wanted to make anyone cry that hard."
Following their conversation with Kimmel, the couple participated in the traditional newlywed style game that the outspoken host likes to play with all new Bachelor Nation couples who sit down with him -- and the pair did decently when it comes to proving how much they actually know about one another.