Hi lookandbuyme,
Thanks for bringing this issue to our attention. I actually don't recall seeing this behavior before, but I was able to locate a listing using the UPC code you mentioned that exhibits the behavior you described when viewed through the iPhone or iPad. On the other hand, I did not see this behavior when viewing the same listing through my Android based phone.
Upon looking into this further, I actually found that the instances of the UPC code that are displayed in the Product Details (mobile app), Item Specifics (mobile website) and Detailed Item Info (mobile website) sections are impacted in the same manner, and not just the reference to the UPC code within the description.
For example, if you look up the item in question through the eBay mobile app and click the “Product Details” section, you should find that the UPC code there is also treated as a phone number. Similarly, if you look up the item on eBay's mobile website, the same will be true for the instances of the UPC code that are present in the Item Specifics and Detailed Item Info sections above the description.
Based on the research and testing I have done, it appears you can potentially prevent this from happening for references like this within your descriptions by adding the following code to the top of the description HTML of your listings:
<meta name="format-detection" content="telephone=no">
However, we do not have the ability to add similar code to the UPC numbers which are displayed in the Product Details (mobile app), Item Specifics (mobile website) and Detailed Item Info (mobile website) sections, so I can only recommend contacting eBay's Customer Support team to make them aware of the issue and see if they can offer a solution.
Of course, the fact that the automatic phone number detection feature on the iPhone and iPad is incorrectly treating UPC codes as phone numbers is unfortunate, but that issue lies within the automatic phone number detection feature on those devices and is outside our control.
I hope this helps.
-Mike