There is only 1 word in the Quraan that falls into the category of Medd Laazim kalimati mukhafaf, being al aan...

Question
There is only 1 word in the Quraan that falls into the category of Medd Laazim kalimati mukhafaf, being al aan.  In reading the chapter on this topic, it states that the medd must be 6 counts in length.  However, in the section regarding Hamza tul wasl, it says that this word can be read with tas-heel, thus being only 2 counts.  Does this mean that this medd is therefore not actually a compulsory lengthening, but can be read either way?
Answer
The word (found twice in surah Yunus) with the questioning hamzah preceding the noun starting with  is read two ways, in both ways the hamzah wasl after the questioning hamzah qata3 is changed in that the hamzah wasl is changed into an alif, or read as a hamzah read with .  When the hamzah wasl is changed into an alif we have a medd letter followed by a sukoon with no shaddah, which is .   When we change the hamzah al-wasl into an alif, the medd is compulsory. 
When however the hamzah wasl is read as a hamzah with   there is no medd, meaning it is not lengthened at all.  The hamzah is read as between an alif and a hamzah and there is no medd letter here.    Some scholars call this qasr meaning no medd in this case, but they do not mean two vowel counts.  When we change the hamzah al-wasl into a hamzah read in between a hamzah and an alif there cannot be a medd. 
So both ways are allowed in Hafs 'an 'Aasim min tareeq Ash-Shaatibiyyah, but when we change the hamzah al-wasl into an alif we must lengthen the medd six vowel counts. 
Please see:
http://www.abouttajweed.com/hamzah-al-wasl/hamzah-al-wasl-lesson-8.html