Odd Spectral Shepherd/support bug

I had 1 Harbinger of the Tides in play, Fertle Thicket, and Nissa's Pilgrimage.

My opponent (Gideon1) had a Spectral Shepherd, which was 6/6 because of a Sword of the Animist, and a Suppression Bonds disabling my Harbinger.

On my turn, I made a white match, which destroyed both the Suppression Bonds, and the Sword of the Animist, both of which had been on 1 strength.

The Spectral Shepherd became a 6/8.