I will cherry pick selections for an alpha read. Mostly when I want people to read it, it's because I have an overarching question such as: "does this idea work?" or "Is the voice I'm using appropriate for the scene?"

I used to let my spouse and family be my alpha readers, but I found as I got their feedback I was revising before the writing was done. Now I don't even like to write when other people can read it over my shoulder. I have gotten paranoid that I'll hear them make some kind of little noise when they catch a run on, or sentence fragment. Maybe that "huh interesting" means they just got to a huge world building info dump that I know will get cut, but exists because I, as the writer, need to know that information.

I know myself, if an idea isn't in writing, it doesn't exist so my draft is full of bracketed notes to myself some of the following are in my WIPs:
[Consider changing this character's gender]
[Does MC need a love interest?]
[Come up with song lyrics to a song about the forest]
[Insert meaningful quote about the pointlessness of violence]
[Need a common name for magical realms here]
[Best Friend, needs name]

I don't mind sharing the notes themselves, Some of these questions turn into threads on this forum. Someone reading the draft, they'll want to offer their thoughts on it, and suddenly it's a conversation topic about the entire direction of the story and becomes a collaboration. Not that there's anything wrong with collaborative work, just if I'm writing something there's a vision I have of what story I want to tell and a surprise collaboration may pull me away from it.