Two televisions with the same model number can behave differently on the same test image. The reason is that a model number does not always specify a single panel.
Why a maker uses more than one supplier
Display panels are made by a small number of very large plants, and a brand selling millions of units cannot depend on a single supplier's output.
Second sourcing protects against shortages, factory shutdowns and price increases, and it gives the buyer leverage in negotiations that a sole supplier would not permit.
The panels are specified to the same tolerances, so both meet the published figures, but tolerance bands are wide enough to leave visible differences behind.
Where the differences show
Panel technologies differ in how they handle contrast and viewing angle, and those two properties tend to trade against each other in opposite directions.
One construction produces deeper blacks that wash out when viewed from the side, while another holds colour off-axis but shows a paler black in a dark room.
Response time, backlight uniformity and how the surface handles reflections vary as well, and none of those are captured by a headline specification.
Why the specification sheet does not resolve it
Published figures are typically stated as ranges or as typical values, which both panel types can satisfy without being equivalent in use.
Contrast ratios in particular are measured in ways that differ between manufacturers, so the same number does not always describe the same behaviour.
Panel type is rarely printed on the box, and where it can be identified at all it is usually through a serial number or a service menu.
Variation within a single panel type
Even units built from the same supplier's panel vary, because uniformity depends on manufacturing consistency across a very large sheet of material.
Backlight bleed, clouding and slight tints in dark scenes are the common expressions of this, and they are graded against a tolerance rather than eliminated.
Manufacturers set a threshold for what counts as a defect, and units within that threshold ship normally even where a buyer can plainly see the variation.
What this means when buying
Reviews describe the unit that was tested, so a review remains useful for firmware, features and build while being less reliable about panel behaviour.
Return terms therefore carry unusual weight in this category, because assessing a screen properly requires viewing it in the room where it will live.
Checking a new screen on dark and uniform test images in the first days of ownership is what catches the differences while the return window is still open.