This look is not just one slider move. From the answers, the photo’s histogram actually shows both a lifted black point and some clipped highlights: shadows don’t reach true black, most tones sit in the brighter range, and there’s also a spike at the far right for blown highlights.

What creates the dreamy feel:

• lift blacks / fade the black point so dark areas go gray instead of deep black
• keep most tones bright overall
• allow some highlights to go very bright or clip
• use selective focus: the foreground subject is sharper while much of the background is softly blurred
• choose the right scene: sunny, attractive, nostalgic locations and tight framing that leaves things to the imagination
• avoid neutral-looking auto white balance if you want a warmer or more stylized mood

So yes, lowering highlights/whites slightly can be part of the edit, but the example isn’t defined by preserving every highlight. Subject matter, composition, bright light, color temperature, and shallow depth of field are all major parts of the effect.