What do you do when two team members give you completely different status updates on the same task?

An important situation.
I would avoid starting with which person is right and begin with what each one means by “done.”
Both updates may be accurate from different perspectives if one is reporting local progress and the other is assessing the deliverable’s readiness for integration or acceptance.
The fastest way to establish the real status is to review the observable evidence, dependencies, and agreed completion criteria together.
If two people can confidently report incompatible statuses, the deeper issue may be less about communication and more about the absence of a shared definition of progress.

Almost and barely are too subjective and relative. Ask them to quantify the actual effort remaining rather than what is already done. Having a clear "definition of done" will help. Also if their opinions differ so much then are they really working together effectively? Maybe some peer-review is justified.

Good question, Syed. When this happens, I usually go straight to the deliverable itself rather than relying on verbal updates — a quick look often reveals the real status faster than debating who's right. Then I ask both to walk me through their definition of "done" for that task, since mismatches like this are often just different understandings of scope, not dishonesty.

Syed, it sounds like the project plan contains some ambiguity.
What verb choices did you use in the project plan?

When you used the word “task,” I thought the project plan might be micro-managing. That task might not really collaborative, so unsure why two people would be assigned an obscure, not-worth-documenting task.

When you used the word “deliverable, I thought of assignments Draft, Review & Revise, Approve, Distribute.

To take an example, let’s assume your scenario is that both of them are assigned Review & Revise.

Person A says they are almost done.
Person B says they are barely started.

I believe what matters is whether either person wants to postpone their target completion date. I think the real status is whether the target completion date must move.

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You didn’t mention interdependencies or critical path (so no obligation to respond) although I admit I’m curious whether this “task” or this “deliverable” … A) has interdependencies easy to identify or B) is on the critical path of the project.

VUCA cultures have interdependencies that resemble spaghetti code, so often, a critical path is just too difficult to identify or take seriously. When executives are competent about the concept of critical path, they start getting interested in simplifying culture, project plans, and interdependencies. But many executives care about business outcomes (behind the glass) not decision latency (in front of the glass).