Challenge 2: The Same Cell, Two Simultaneous Values — Solution Walkthrough

What you'd expect to happen:

The cell ends up showing only ONE of the two values — typically
whichever edit's update reaches the server last — rather than some
combination or interleaving of both people's input. The "losing"
edit simply doesn't persist as the cell's final value.

Why this differs from two people typing in the same paragraph of a shared Doc:

Chapter 2 described text edits merging because a paragraph is a
flowing SEQUENCE of characters — two people typing in different (or
even overlapping) positions within that sequence can have their
individual keystrokes interleaved correctly, since each keystroke is
just one more character being inserted somewhere in an ongoing
stream. A spreadsheet cell, by contrast, holds a single, atomic
value — there's no equivalent "sequence of positions" for two
different complete values to be interleaved into. The cell's content
either becomes one person's value or the other's; there's no
meaningful way to "merge" two entirely different numbers or text
strings the way two people's separate character insertions into the
same sentence can be combined.

WHY THIS WORKS AS AN ANSWER
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This is exactly the distinction this chapter's own warning box draws:
Chapter 2's merge behaviour depends on content being a flowing
sequence that can be interleaved — a cell's single atomic value
structurally cannot be interleaved the same way, which is why Sheets
resolves a same-cell conflict by picking a winner rather than
attempting to combine both edits.