True.
Alpha readers are generally your editor, in a sense, because if he or she is providing feedback on your partially finished or drafted work while constructing commentary regarding the overall theme of your writing/novel, then they're also an alpha reader. Like they'd give feedback on what's working or what feels weak in the overarching theme of your story. For example, the pacing at the start feels weak and needs to be more punchy, or the plot is great until you swing the story to the far left of the totem pole, where it suddenly shifts into a dramedy that feels off---stick to drama.
On the other hand, beta readers are usually used near the end of the finish line. Like publishing companies would hire 3 or 5 Beta Readers then set up a panel interview to get feedback on the drafted manuscript. Their feedback is essential as the penultimate step before the last and final edit before the novel is set to production.
It's also hard to find beta readers willing enough to provide constructive criticism on an unfinished manuscript, ESPECIALLY if they're unpaid. They approach your writing as casual readers, reflecting the entirety of your reader base, where their feedback revolves around inconsistencies and overall character mapping and story plotting like: Is X supposed to be dumbass? X keeps doing the same shit and it's pissing me off. X is great until B shows up. Is X meant to be written like this? If yes, then why?
I have a friend who had a beta reader say to his panel feedback session, "Is your protagonist supposed to be an idiot? He keeps 'curling' his lips. Does he have a tick?" And then he realised upon inspection that he kept putting dialog tags and description as, "he curled his lips" 28x throughout his novel. π
Beta readers are meant to be brutally upfront. Otherwise, you're not getting what you paid for. Because the assumption is, what they're thinking is what your readers will be saying.