Good questions & IMHO this is where things get interesting or tricky depending upon your point of view.
Remember that market cap is a function of total shares and share price. If the market thinks a company is more valuable, then share price goes up. Assuming that total shares are constant, therefore market cap goes up.
Similarly, if the total number of shares goes up without a corresponding increase (or decrease) in share price, then market cap goes up also (assume constant share price). However, this almost never happens as the market notices and share prices will generally go down because the market as a whole (meaning ALL investors) has a general perception of the total value (aka market cap) of a company. This is referred to a dilution because of the corresponding drop in share prices leaving the total market cap about the same.
As far as NioCorp, I think the shelf offering is to provide options to the company (note - not stock options). While I will often be critical of the leadership team for failure to deliver, I do not believe for a moment that they are stupid.
I think that the shelf offering provides a less administratively burdensome means for NioCorp to offer more shares (aka dilute) when needed to raise fund for operations like demonstration plants, studies, and - not least of all - salaries to Mark & team.
It also provides a means for them to offer shares (still called dilution) in case there is a significant possible event. This could be a means to raise funds to cover expenses or maybe if they can get investors or loans which don't cover the full cost of construction.
A big change can be if the company uses the money raised to help the business, then it can be rewarded by an increased share price because the market believes that it is more valuable with the addition of this new business aspect.
Bottom line is the shelf offering is a means for them to sell more shares to the public without having to have a vote or register them with the government for multiple offerings (e.g. they could have 4 offerings of $50m in shares all covered under one process vice 4 processes).
