It's not unusual for aliens to receive UC.  H/L-visa holders, however, are generally no eligible.

From a tax perspective, agree the exclusion should apply since UC is US-ECI pursuant to §§861 and 864 and is subject to tax under §1 and § 55 in accordance to §871(b).  The ARP also does not preclude the availability of exclusion to individuals who file as NRA.

Not sure about PS but Lacerte/ProConnect Tax is doing it right and computes the exclusion on 1040NR.