Tonight's episode of the ABC romance reality show will see Brad taking a group of women including Emily to the Las Vegas Motor Speedway, unaware of her connection to the sport.
She had previously told him that her fiancé Ricky had died in a plane crash just days before she discovered she was pregnant with his child, but has yet to disclose Ricky's involvement with NASCAR.
Speaking to reporters on a recent press call, host Harrison said that Emily had ended up on the date by "happenstance" and urged viewers to reserve judgement on the outing until they had watched the episode.
"Brad has three dates [this week] and Emily definitely is not going to end up on the two-on-one, so she really ends up on this NASCAR date by happenstance," he said. "Now, with that said, we are not stupid and naive. We as producers knew this story, and we had a choice to make - do we tell Brad about Emily's story or do we warn Emily? Our choice is kind of what we've always done and that is let the real life drama and everything play out."
He continued to say that the date had an effect on both Brad and Emily, explaining: "It forced Emily to face some demons that even after five years I don't think she's quite dealt with yet, and then also forced Brad to learn the rest of the story... It kind of forced a lot of issues on many, many different levels. It's unbelievably compelling and intriguing. "
Harrison added that the date forced Emily and Brad to "take a huge step" in their relationship, teasing: "It was either going to blow up in their face and Brad's going to realise, 'Hey, I can't handle this, I can't replace this guy' or Emily will realise she's not quite ready, or they're going to move through it."
As for which remaining bachelorette he thinks is the right match for Brad, he pointed out that the bachelor saw something different in every single person.
"What he is finding in Emily is completely different from what he finds in Chantal and obviously completely different from what he finds attractive about Michelle," he said. "But his sincerity and his attraction to these women is just as sincere with all of them... It's like they all give him a little something different."
He added: "In the end, it's your job to figure out who really completes that picture and who you want to spend the rest of your life with."
The Bachelor airs Mondays at 8/7 on ABC.