How toe cant fit the first long vowel idea ?

_{hello, I have searched} Vowel Digraph on google ~

I even got a very lovely children's song about it ~ “ When Two Vowels Go Walking, The First One Does The Talking ~” I learned that ---Vowel Digraph -- If two vowels are beside each other in a word or syllable, the first vowel is usually long while the second vowel remains silent. Examples of vowel digraphs are:
ai-- maid, ee-- sweet, ea--bean, oa-- boat, ay--tray. This rule does not
apply to diphthongs.



they say Vowel Digraph are ----- ea ai oa ay ee .



My confusion is :



If ue oe ie could also view as vowel digraph ?

As follows :

oe toe shoe

ue blue glue true clue

ie tie pie lie die

I especially want to know

how toe cant fit the first long vowel idea ?


isnt the o of toe sounds like the o of or ?

thanks ~