Double check what they have put in, you dont generally get 5w30 in a semi, it could be they have written it down wrong.
Theres a slim possibility, very unlikely however, that the tech is being pedantic, many current synthetics could not have been called synthetic 20 years ago as they start life as mineral oil, not molecularly constructed from scratch, rather the mineral oil is stripped back to its purest most uniform arrangement then 'put back together' using the resultant 'new' highly uniform relatively pure base oil combined with an appropriate additive pack and some polymers. As such it is now considered to be engineered enough at a molecular level to be classed as synthetic, though it would originally be considered only semi due to its mineral origins.
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