Hass 'cados come in ripe and good mid-winter here. Most of the ones. . . .
You see year round now are from Mexico or South Americe. And they may be picking them too green, because the one labeled as above never seem to have that rich, oily goodness that a good California Hass seems to have.
I think the strings are from being held too long, however the avocados are held to keep them for market. Had your seed sprouted at the root timp? (the wide end of the seed). Old avocados are the ones I seem to see with strings here.