I would have highlighted different key words in your text, starting with this sentence:  Enhanced credibility/ reputation comes from a perception that the organisation is making an investment into the target audience without looking for any blatant return from the target audience.

This leads me in a slightly different direction that establishes a clear border and difference between public relations and marketing: MARKETING is in it for the SALES.  As Cutlip writes its goal is to foster “transactions that deliver products and services in exchange for something of value to the provider” (usually money).

PUBLIC RELATIONS is in it for the RELATIONSHIP. Again, quoting Cutlip:  “the management function that establishes and maintains beneficial relationships between an organisation and the publics on whom its success or failure depends”.

So, yes, you’re right that the goal of marketing PR or, in this case, of inbound marketing, is to draw potential customers, the assumption being that if we enter into a relationship with a person on the basis of though leadership, this person is more liable to become a customer.  BUT:
A)     Not all people drawn into the tough-leadership induced relationship will become customers and this should not be the only measure of success of such an initiative;
B)      These relationships could prove to be beneficial in many non-commercial ways, e.g. good will and support in other issues.

Again, the measure of success of a PR program is the relationship itself, not any specific benefit that might accrue from that relationship in the near future.  This is unfortunately much more difficult to measure than the ROI of an advertising campaign.