Ukraine is trying to preserve some ability to recover population-wise, with sufficient young families in years to come, with Dads in the households. They have a BIG hole in their demographic chart around 20-25 y/o. After Russia grabbed Crimea, and the West did nothing, a lot of the kids as they turned 18 figured Russia would eventually conquer or at least run Ukraine, and wanted no part of that. So they headed for the greener pastures of Europe.
Ukraine's strength of male population is in the 35-45 y/o bracket. In many ways, such men make better soldiers than the younger men, anyway. (This is not 100%, of course.) And most ~40 y/o mens' children are mostly grown to young adulthood, so their losses in many ways affect their descendants less.
So, you and Graham share a similar ignorance. You I can forgive. Graham's staff should brief him better.