Validity and proof are two different concepts. The initial ATP applicant undergoes a logbook review by the examiner prior to the checkride to see if all the requirements are met "validity". I never saw one ask for "proof" such as maintenance logs, etc. Of course it may happen, I just haven't seen it!

Airlines are interviewing applicants who are "close to the requirements" and giving them class dates with the anticipation they will meet the requirements before their hire date. The temptation and potential to falsify logbooks would be a concern to me if I was an ATP examiner and the potential to review the pilot logbooks with a fine tooth comb increases. Especially, if there was 100 hours logged in the past two to three weeks. Is flying that many hours in such a short time doable? Of course! My suggestion was to simply file a flight plan for added "validity".