An example video: https://youtu.be/lXp7_Sjgm34?t=273
For example "I read to my son" could be pronounced two different ways depending on tense. "I read", vs. "I red".
There are other examples too, off the top of my head "I polish my shoes", vs. "I have a polish friend.". Or "the bow of a boat", vs. "at the end of the play the actors take a bow".
But that's not what's going on in the Swedish example above. The vowels are exactly the same between "anden" (the spirit) and "anden" (the duck), but the pitch accent is different, the "song" of the words is different.
Here's a video showing the difference:
https://www.youtube.com/watch?v=lXp7_Sjgm34
(And if you can't hear the difference in that video, don't worry too much, it's Swedish that's weird, not you. :) )
I am wondering about your accent, though, because, to me, "bow" is pronounced the same in both of those examples. Robin hood shooting an arrow from his bow, however, has a different pronunciation which is the same as the bow tied on my present.
https://www.dictionary.com/browse/bow agrees indicating IPA baʊ for both.
I just assumed they meant bow as in bow and arrow. The other example I did not know. "Read before you think before you write".
Ever-relevant poem: http://ncf.idallen.com/english.html
English is kind of a hot mess.
I do understand this sound on a cognitive-analytic level (some phonetics courses at university help when learning sounds). I can pronounce it, at least passably.
There are big regional variations to pronouncing sj and so on. Fine, I can live with that, just pick one and use it consistently, preferably that of your teacher.
But when it comes to the sound the article is about, I hear something else.
At some point I cut together many instances of words with that sound from Swedish pop songs and told my teacher which sound (IPA) I clearly hear in all those instances. She told me flatly that I'm wrong. Those singers clearly sing another IPA sound.
It must be similar to when Russians try to show me the difference between hard and soft consonants. They tell me they really over-pronunciate now and they sound starkly different, I'm not even sure I hear a difference.