This install fits in the "close, but no cigar" category.
Using the flex, I see no need for the 45 before the 90. Hence, no need to take that chunk out of the structural steel.
(There's a time, place, and method to cutting structural steel ... but this is not it!)
I'd like to see some support for that flex as well.
A few other notes:
Even were the conduit steel, a ground wire is necessary. A neutral is not (on the feed side).
For the life of me, I cannot imagine a situation where you would NOT want a neutral to the secondary panel.
I do hope there's a main breaker in that panel.
I do hope the transformer is grounded, including on the secondary side. Grounded both with a wire back to the GEC, as well as to that structural steel.
Likewise, the neutral buss ought NOT be bonded to the case ... your 'bond' is at the transformer.
Now ... into "forbidden territory." While the NEC has information as to sizing conductors and breakers, I've never seen an inspector check them. This job has enough signs of a well-intentioned, but unqualified, job that those decisions ought to be reviewed.
I also agree; a three phase panel fed by a single phase transformer is a worry. I consider it a technical violation of code (look at the panel listing).
