The same field of vision
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The requirement
Brand name, class and type designation and alcohol content must be positioned so that all of them can be viewed simultaneously without the need to turn the container.
Which is not the same as "on the front label"
It is a statement about what a person can see from one position. A wrap label that carries the brand at the front and the alcohol content around the curve fails, even though both are on the same label.
How much of a round bottle you can see
Appreciably less than half the circumference, because the curve turns away. Treating the printable area as the field of vision overstates it, usually by enough to matter.
Alcohol content is the one that drifts
It is small, it is unglamorous, and it is the element a designer will move to the back or the side to clean up the front. That move is the violation.
Class and type has to be legible as well as present
It is the statement of what the product actually is. Setting it very small beneath a large brand name satisfies the geometry and invites a different question.
Square and flask bottles make it easy
A flat panel has an unambiguous field of vision and the whole panel is in it. For a producer who wants a lot of front-label copy, that is a reason to prefer a flat-sided bottle over a round one.
Check it on the bottle, not the artwork
Print the label, apply it to the actual container, stand it at arm’s length and look. The flat artwork cannot show you what the curve hides, and this is a two-minute test.
A neck label does not rescue it
Moving the alcohol content to a neck label puts it on a different part of the bottle at a different radius. Whether it is in the same field of vision as the brand name is a question to answer by looking rather than by assuming.
Decide the bottle shape with this in mind
This requirement is one of the few that genuinely favours one container geometry over another. If the front panel is going to be crowded, a flat face is worth more than it looks.