In case anyone was still curious, I finally received a response from the record keeper:
"Although there is no direct guidance on this issue, the statutory rules and other guidance applicable to plan administration require plan administrators to proceed in the best interest of the plan and participants. By consistently moving small balances to the plan forfeiture account, the plan saves administrative costs, retains dollars in the plan, and reduces transaction costs, thus furthering the objectives set out in ERISA and other regulations".
This particular record keeper bills the plan sponsor a per participant fee - the fees are not deducted from plan assets. The forfeitures are also being used by the employer to offset matching contributions. I subsequently pointed this out and that the practice of forfeiting small balances is acting in the best interest of the employer, not the plan or participants. I doubt I will get another response. I am going to pass along to my client the advice from Lou S: