HMG assault value when in an assault vs tanks

[Blackcloud6]

I just had an interesting situation.  Two US infantry platoons, a leader and a HMG unit assault a Panther platoon which was alone.  The infantry chose to fire AT weapons.  So how does that leave the value of the HMG unit?  The rule says to half the HMG unit if it assaults unless another infantry-type friendly unit is a participating in the assault.  So, the way I read this, although the two infantry platoons chose to fire AT they are still "participating in the assault" and the HMG would not be halved.

This also made me realize it would have been better to just assault with out any units firing AT weapons and just get the larger assault value against the Panthers.  I'll post a different post on that notion.