All applicants may present impressive documents during job application. And for welders, these documents are just secondary. Welders always have a Trade Test in order to prove their welding skill.
With regard to the fake certification, I think the company involve must be informed that there where false documents that have been circulating with respect to Welders Qualification Test documents. They must be aware that their company was being used and it should be stopped. I think there's nothing wrong with that.
If you are the interviewee, it is your right to question the applicant if you have doubts with the documents that they are submitting.
Conclusion:
If you have doubts over the submitted document, you may reject the applicant or you may accept but he/she will undergo a Qualification Test. If he/she passed the test, it will be you decision if you will hire them or not. If the welders will be coming from a contractor, you have the right to question the credibility of the contractor with regard to the documents and welders they were providing.
I believe that there's always a need for a trade test in every project especially for the new employee (welder).
Note: This is my own opinion with regard to the matter.
(Please refer to ASME IX - Welder Performance Qualification
QW-322 EXPIRATION AND RENEWAL OF QUALIFICATION
QW-322.1 Expiration of Qualification. The performance qualification of a welder or welding operator shall be affected when one of the following occurs:
(a) When he has not welded with a process during a period of 6 months or more, his qualifications for that process shall expire; unless, within the 6 month period, prior to his expiration of qualification
(1) the welder has welded with that process using manual or semiautomatic welding, under the supervision and control of the qualifying organization(s) that will extend his qualification for an additional 6 months
(2) the welding operator has welded with that process using machine or automatic welding, under the supervision and control of the qualifying organization(s) that will extend his qualification for an additional 6 months
(b) When there is a specific reason to question his ability to make welds that meet the specification, the qualifications that support the welding he is doing shall be revoked. All other qualifications not questioned remain in effect.