This seems to be a hangover from the original screenplay, where the gate was theoretically capable of being opened (and traversed) from both sides, but couldn't transfer people because the beam length was so short that anything entering from the Abydos side wouldn't make it back to Earth before the gate shut down.
The plan was to open the gate for the minimum period possible and then close and evacuate the missile silo entirely. They'd only unlock if the team made it back safely under their own steam.
GENERAL WEST: But I won't send our boys over there if I'm not absolutely sure I can bring 'em back.
ASSISTANT LIEUTENANT: We know the beam will only stay connected for a short amount of time. After the ring shuts itself down, we'll have to re-establish the beam
from the other side.
DANIEL: We could re-establish from here.
GENERAL WEST: Once our team goes through, this place will be evacuated and sealed. We don't know what might come through from the other side.
DANIEL: So you want me to go over with the team, re-align the Star Gate and
bring everyone back home.
In the movie, it would appear that Feretti is the only one who bothered to read the briefing materials. It was established in the previous scene that Daniel needed to open the gate from the other side.
WEST: That's why we may have to abort. This project is for naught without a reconnaissance mission.
JOHNSON: Once on the other side, we'd have to decipher the markings on their 'gate, and in essence dial home in order to bring the team back.
WEST: Based on this new information, I don't see how we can do that.
The official novelisation agrees with this sentiment. Johnson (AKA Reilly) is basically a big dumb dope who didn't do his homework.
'He's right," agreed Reilly, looking up from hammering the tent
spike. "If we're not back soon, they'll just turn the Gate on from
Earth." "Look, dimwit," Feretti began to lecture Reilly, "ask
yourself how you got here. Was it a two-lane highway? No. You got
blasted through this weird energy cannon at about fifty billion miles
an hour, turning you into a higgin' zeromass, interstellar Gumby,
okay? Now think: how many directions were you going at once? One!
Now, not only is the silo emptier than a church on payday, but even if
those science boys do go back inside and even if they do turn that
goddamn galactic garbage disposal back on, what are you gonna do? Swim
against the current?"
Science Officer Brown was listening. He looked up from assembling the
dish scanner and said, "Feretti"s right. The beam moves one direction
at a time. This is deep shit we're in."