That is interesting.
Am I right in thinking that at some point it really was stylized (but not abbreviated) as "POP Trading Company" and then it was changed to "Pop Trading Company" later?
There are multiple websites referring to the company by 3+ variations of its name, and they're not random spam sites either. The official Converse website, END. Clothing, and other real online stores show both "POP/Pop Trading Company" in different parts of the websites.
The breadcrumbs on END. Clothing's category page for the company are displayed as:
Home > Brands > Pop Trading Co...
But this is only a display issue. If you inspect it, the full name is in the code:
<span property="name">Pop Trading Company</span>
I think the same is happening on Google, because you'll notice it doesn't abbreviate the name when that same page shows as a "normal" result (not as those small sitelinks). Google has decided that a shorter title is more appropriate only in that specific position.
Search for "site:poptradingcompany.com" or any other search that the webshop ranks for, and you'll see the full title as you expect when it's displayed as a normal result.
Anyway, Google doesn't guarantee it will use whatever title you choose. If it thinks it has a better title for the page, that's what is used. In most cases it's because of keyword stuffing and/or misleading titles, which doesn't seem to be the case here.
I think it just wants a shorter title in that position and it's "smart" enough to know how to abbreviate commonly displayed words like that.
Possible solution: If you're the admin for this website, find out why Google can't find/read any rich results from this page. Make sure robots.txt isn't blocking Google from accessing anything like rich results / structured data. You may be able to convince the machine to use the correct title.
Also, it doesn't like that the title is the same for both the webshop and the base domain when shown together like that. If the above possible solution doesn't get the desired results (after implementing and waiting some time for Google to update) then try giving them each a unique title.
EDIT: I think think the titles should be made unique first, before doing anything about the rich results. Decide which page you'd prefer to rank higher for "Pop Trading Company" - the webshop or the base domain.