There is no vague meaning. Perceive means detect. Blindsight does not say "detect location", but perceive surroundings as in everything. Stealth doesn't work against them within the range. It's not a vague rule. Not sure why anyone is trying to make it one. There is no Blindsense and Blindsight now.
You can stealth on someone with truesight. But not Blindsight. Nowhere does it say perceives with hearing. So moving silently is irrelevant.
At this point in time barring any clarification from the developers, if you are within a dragons Blindsight range it knows you're there whether Stealthing, invisible, or what not. It's not even something open for discussion unless you're somehow arguing the meaning of the word perceive.
Here are the relevant passages:
"Blindsight: A monster with blindsight can perceive its surroundings without relying on sight, within a specific radius."
"You can’t hide from a creature that can see you, and if you make noise (such as shouting a warning or knocking over a vase), you give away your position."
First off, there's a pretty clear difference IMO between see and perceive. Blindsight is by definition a way to perceive without seeing. So when it says, "you can't hide from a creature that sees you," I don't think it automatically extends to blindsight.
I think that what blindsight actually does is vague. There are certain reasonable interpretations that occur to me:
1) Blindsight works exactly like regular sight, except you can do it with your eyes closed and/or in the dark. Line of sight rules are unchanged. In this case, blindsight's main utility for dragons is that they can fight in the dark at no cost, even if it's totally pitch black. The support for this interpretation would be to argue that since it just says you perceive without relying on sight, all perception rules are the same as before, all that changes is the mode of perception.
2) Blindsight is a special sense that works differently from vision. In this case, each particular instance of blindsight is actually different, and blindsight is more of a category than a clear term. It is left to the DM to decide how each instance of blindsight works. The DM can and should adjudicate based on his/her own sensibilities how one goes about hiding from a creature that can "see" with hearing or smell.
3) Blindsight is an automatic "detect everything" ability. The creature automatically perceives everything within the radius, regardless of circumstance.
I simply don't think there's enough in the text to clarify these from each other. I wish there was more clarity (I'm not a "vagueness is good" fan), but I just don't see it in the text.
Personally, given what we have, I think option 2 is the most interesting, and it's how I plan on running creatures with blindsight. It makes me do a bit more work, but the play at the table will be a lot more fun for it. I also don't like the idea that a single ability completely shuts down a major rogue specialization. I would rather use blindsight to engage the rogue than tell them they don't get to do fun things this fight. I wouldn't say option 3 is a terrible choice either though. I just don't think there's enough to be able to argue RAW is clear one way or the other.