A guru once declared that Access determines the data type based on x number of Excel rows. IIRC that number is somewhere around 10, so your data or it's format in any number of rows within that range could be the difference.
If this is an issue, better to link the sheets and use append/edit queries on native Access tables that are basically copies of the sheets. Once created and formatted, the table data types will always be correct when retrieved from the tables. All that notwithstanding that sheets often make for poorly designed tables. To go further, I'd try to make the tables properly normalized rather than just reproduce sheet structures. If that isn't clear, best to research db normalization to see why sheets usually make lousy tables.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.