Some spell and ability descriptions are poorly worded and haven't been corrected but the first sentence of a spell or effect can sometimes be considered a mere description of the effect, rather than a fully accurate rule about how it is to be applied. I'm NOT going so far as to say it's flavour text as that opens a whole can of worms with some people.
But if you consider it as merely a descriptive opener to the spell, a teaser if you will, then you get into the meat of the rules in the next sentence and after.
For comparison I'll use the Rogue Evasion ability, which suffers from the same problem:
Beginning at 7th level, you can nimbly dodge out of the way of certain area Effects, such as a red dragon's fiery breath or an Ice Storm spell. When you are subjected to an Effect that allows you to make a Dexterity saving throw to take only half damage, you instead take no damage if you succeed on the saving throw, and only half damage if you fail.
The first line mentions "area effects" and even gives two examples of attacks that are area effects. But it then goes on to omit the word "area" from the rest of the description and during the actual explanation of how the ability works.
What to do?
I think the simplest, and most consistent approach to consider the first line as just a summary of the spell/effect/ability and nothing more than that.
This makes sense as many, many spells have a first line that adds nothing beyond a brief description. Melf's Acid Arrow, for example, starts with:
A shimmering green arrow streaks toward a target within range and bursts in a spray of acid.
But in this case, it doesn't include anything that could be interpreted as an actual game mechanic and so doesn't cause a problem.