Unexpected CAST decimal Value Objects to decimal(18,2)

Question

I have a value object named "WithdrawFee"

public Fee WithdrawFee { get; private set; }

and the Fee value object is :

public class Fee : ValueObject<Fee>
{
    public decimal Value { get; private set; }

    public static Fee FromDecimal(decimal value) => new Fee(value);

    public Fee(decimal value)
    {
        if (value < 0)
            throw new ArgumentException("Fee is not valid");

        Value = value;
    }

    public override int ObjectGetHashCode() => Value.GetHashCode();
    public override bool ObjectIsEqual(Fee otherObject) => Value == otherObject.Value;

    public override string ToString() => $"{Value}";

    public static implicit operator decimal(Fee fee) => fee.Value;
}

that configured with fluent bellow :

builder.Property(c => c.WithdrawFee)
.HasConversion(c => c.Value, v => Fee.FromDecimal(v)).HasColumnType("decimal(18,8)");

THE PROBLEM:

the problem is when I run query below :

decimal testValue = 10.541m;

var result = await db.Networks.AsNoTracking()
.Where(c => c.WithdrawFee > testValue )
.ToListAsync();

it ran this sql query on db (I got it from sql profiler):

SELECT *
FROM [Networks]
WHERE CAST([WithdrawFee] AS decimal(18,2)) > CAST(10.541 AS decimal(18,2))

as you can see, it cast values to decimal(18,2) !

Why ef cast decimals ?

How can I fix this ?

ef core version : 5.0.10

.net version : 3.1