UsCIS officer probably says you cannot turn TPS to greencard is because he was probably thinking not graduated F1 people, crossed mexico border people or even B1/B2 who doesn't have proper degree or asylee people . like i said he goes by book a to b rule not how to interpret it . but if you have american bachelor/master degree , overstayed and have sponsor to file GC you can adjust after tps. if you dont know how? a good smart lawyers will do it. for you. in fact tell you the truth people who had stem master degree was able to adjust status just paying some fine even before this tps thing.