Tags not fully working as expected

Dear readers,

First of all, thank you for this plugin and also taking the time to read my issue/question.

I have a question related to ‘tags’. I want to use those to optimize my related products, which are shown on a single product page.

At the moment I use 2 sections for this, because I’m trying stuff out. First this ‘Woo Related Products’ (which is set to use ‘tags’ instead of categories) and beneath that, the default Woocommerce related products (which I also add code for, to show only products based on tags).

However both sections are not displaying the related products that I would expect. Let’s say I have these products (sorry it’s in Dutch, otherwise it doesn’t make sense):

– Pokemon armband (rood) per stuk
(the tags I gave to this product are ‘pokemon’, ‘armband’ and ‘merchandise’)

– Pokemon armband (blauw) per stuk
(the tags I gave to this product are ‘pokemon’, ‘armband’ and ‘merchandise’)

– Pokemon armband (geel) per stuk
(the tags I gave to this product are ‘pokemon’, ‘armband’ and ‘merchandise’)

– Pluche Minion Dave +/- 16 cm (nieuw)
(the tags I gave to this product are ‘pluche’ and ‘merchandise’)

– Assassin’s Creed sleutelhanger met logo en Skullhead
(the tags I gave to this product are ‘assassins creed’, ‘sleutelhanger’ and ‘merchandise’)

Now this happens: when I navigate to the first product of this list (the red pokemon bracelet or in Dutch ‘rode Pokemon armband’), I expect to see at least the blue bracelet (and the pink and yellow one, which are also in the store). Because these products share exactly the same 3 tags! That should be a perfect match right?
However, I see maybe one of them, but mostly other merchandise products like dolls, t-shirts, keychains etc. And of course, this is probably because they share the same categorie (‘Others’ or in Dutch ‘Overig) and they share 1 tag together called ‘merchandise’. But still, shouldn’t the related products show the best matches? So when most tags are the same?

Or is it maybe because I’m only showing 4 items, so there were maybe better matches found, but the best match is not always on top?

Does anyone have an explanation for this? Maybe my way of thinking is not right and I could also not find similar issues from people online, so I’m curious of how this should work.

Thank you in advance!

The page I need help with: [log in to see the link]