That is sloppy writing!
A good practice is to explain the acronym at least once at the beginning of the text, so your readers know what it means, and then use it the same way you would the full phrase that it replaces. For example:
The Internet Content Adaptation Protocol (ICAP) was proposed in late 1999 by Peter Danzig and John Schuster. The ICAP specifies extensions ...
If your text is long, it may be a good idea to repeat acronyms every now and then, for example, at the beginning of each chapter or section, or if you haven't used it for some pages, especially if the acronym is not well known or one you invented for your text:
Peter S.
Stack Exchange Questions and How to Ask Them
Chapter 1
To ask a good Stack Exchange question (SEQ), you first need to think about what you want to know. Users are irritated by vague or lazy SEQs, and won't want to help you with them. But first, let us look at what Stack Exchange (SE) is. Chapters 1 to 11 will give you an introduction to SE, then chapters 12 to 86 will focus on SEQs.
... [other chapters] ...
Chapter 12
Every Stack Exchange question (SEQ) can be up- or downvoted. There are many SEQs that receive no upvote at all.
If an acronym is globally (!) well-know, such as BMW, UK, or cm, you don't have to expand it, but if your acronym is only well-known to your expert audience, explain it at least once, because texts targeted at an expert audience are often ready by experts from related fields, journalists, and the lay public, and you don't want to be unnecessarily obscure.
If you don't explain an acronym and it is well-known, nevertheless use it as if you were writing the full unabbreviated phrase:
Wrong:
The UK kingdom, despite its name, had a Queen.
Correct:
The UK, despite its name, had a Queen.