Telegram's HD photo option and a locally prepared high quality file are different parts of the workflow. This tool controls the crop, dimensions, and encoding of the file you download. Telegram controls how a photo is sent after you select it. Choosing a larger local export does not automatically turn on the HD option in the app.
Telegram introduced HD photos as an alternative to its standard photo route. Check the current sending controls on your device. If the receiver needs the file itself rather than a photo preview, consider sending the prepared image as a file instead and verify that you selected that route.
This page uses our 2560×2560 bounding box. The photo keeps its original proportions inside those bounds; it is not forced into a square. The dimensions are our export choice for a detailed working copy, not a promise about every image version Telegram stores or delivers in every client.