I can reproduce this in Terminal.app, macOS 15, both on Node.js v23.6.0 and Node.js v20.12.2.
Whenever it is the red heart's turn, the following text shifts left by one character width.
It happens with multiple fonts and at all font sizes I tried.
In the spinners.json file, each entry appears fine at glance. Just in case there were invisible characters, joiners, or unusual unicode combinations going on, I re-created the array from scratch using the Finder's emoji picker and added one space after each, but the same issue remains, and indeed only on the red one, regardless of placement in the sequence.
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