I think a lot of pole barns are built with the floor last. Out here, tax wise, we have the same situation when including water or electricity in an out building.
The decision you'll need make may be based on if you ever expect to have the inspector back to look at an addition, or something else, on that pole building. Then if he catches you've added a concrete floor you may be liable for the permit plus fines. The fine here is double the permit fee.
One thing for sure, if you do the floor without inspection, take good photo documentation in case the issue arises in the future or you want to convince a prospective buyer the job was well done even though not done under the building permit.
Here too we'd need to disclose the non-permit floor to a prospective buyer. Even if you plan to keep your place "forever" someone at sometime may need to deal with this.