Why it happens at the forms, not later
Honeycombing is a placement problem, not a curing problem or a weather problem. It shows up the moment forms come off a wall or a column, because it was already there before the concrete ever set. A tall form packed with reinforcing steel gives concrete very little room to move, and if the mix cannot be vibrated all the way into every corner, air and stiff material get trapped against the steel and the form face instead of flowing around them.
Congested rebar makes it worse. A footing dowelled into a wall, a corner with two bars lapped and tied, or a blockout for a sleeve all crowd the space the concrete has to fill. So does a mix that is too stiff for the reinforcement it is going around, or a lift poured too tall and vibrated only near the top. Walls go in lifts for exactly this reason, with each one worked before the next one lands on top of it.
Honeycombing versus spalling
These two get confused because both leave a wall or a slab looking rough and pitted, but they come from opposite ends of the job. Honeycombing is there the day the forms strip, a void left behind because concrete never fully surrounded the steel or filled the form in the first place. Spalling shows up years later, after de-icing salt, a poor finish, or repeated freezing and thawing works the surface of concrete that was placed and consolidated correctly to begin with. One is a forming and placement issue you catch on day one. The other is weather damage that builds up over winters. Mixing the two up leads to patching the wrong problem for the wrong reason.
What shallow honeycombing needs, and what it does not
Depth is what decides the fix. Honeycombing that only nicks the surface, without reaching the reinforcing steel, is usually a cosmetic and durability repair: chip back to sound concrete, clean it out, and patch with a bonded repair mortar so water cannot keep working into the void from there.
Honeycombing that opens up around the steel is a different conversation, because exposed rebar rusts, and rust takes up more room than the steel it came from, which can push a surface patch back off the wall it is bonded to. That depth of honeycombing is worth a look in person rather than a guess over the phone, especially on a foundation wall carrying real load.