[mxmxnxor]

HTTP compression (gzip, brotli) works on byte/text level and doesn't know about your markup template repetition (where structure is mostly the same but small changes everywhrere) so it will be not as efficient as manual template-data separation. Moreover you can also use gzip, brotli for your template and data so http compression doesn't change the overall picture

[potatoz2]

It changes the overall picture because HTML compresses better than JSON, which itself compresses better than your deduped arrays (because of the duplication you’re trying to avoid). So the HTML would be closer in byte size to the most compressed version you’ve shown than it appears, after compression.