Insert not reflecting correct datatypes

[Tasteful]

Table that is created by EF Migration

CREATE TABLE [Products].[BaseProductFieldData](
	[OwnerSystemId] [uniqueidentifier] NOT NULL,
	[FieldDefinitionId] [nvarchar](100) NOT NULL,
	[Culture] [nvarchar](10) NOT NULL,
	[Index] [int] NOT NULL,
	[BooleanValue] [bit] NULL,
	[DateTimeValue] [datetimeoffset](7) NULL,
	[DecimalValue] [decimal](18, 2) NULL,
	[GuidValue] [uniqueidentifier] NULL,
	[IndexedTextValue] [nvarchar](250) NULL,
	[IntValue] [int] NULL,
	[JsonValue] [nvarchar](max) NULL,
	[TextValue] [nvarchar](max) NULL,
	[LongValue] [bigint] NULL
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

Generated SQL Insert from SQL Profiler

exec sp_executesql N'SET NOCOUNT ON;
INSERT INTO [Products].[BaseProductFieldData] ([OwnerSystemId], [FieldDefinitionId], [Culture], [Index], [BooleanValue], [DateTimeValue], [DecimalValue], [GuidValue], [IndexedTextValue], [IntValue], [JsonValue], [LongValue], [TextValue])
VALUES (@p6, @p7, @p8, @p9, @p10, @p11, @p12, @p13, @p14, @p15, @p16, @p17, @p18);',
N'@p6 uniqueidentifier,@p7 nvarchar(100),@p8 nvarchar(10),@p9 int,@p10 nvarchar(4000),@p11 nvarchar(4000),@p12 nvarchar(4000),@p13 nvarchar(4000),@p14 nvarchar(250),@p15 int,@p16 nvarchar(4000),@p17 bigint,@p18 nvarchar(4000)',
@p6='09AE36A4-6146-4838-9617-533F8E7C0406',@p7=N'FieldDefinition0',@p8=N'aa-DJ',@p9=0,@p10=NULL,@p11=NULL,@p12=NULL,@p13=NULL,@p14=NULL,@p15=NULL,@p16=NULL,@p17=NULL,@p18=N'4c6b5aba-6427-4f07-9753-7c831dbf788e',@p19='D5343606-E6B7-4CC6-93E3-89F7321703E2',@p20='09AE36A4-6146-4838-9617-533F8E7C0406'

If we check the parameter types and compare them to the datatype that the table is specified with, check @p10 to @P13. What is the reason to use nvarchar(4000) for a nullable bit field?

@p6 uniqueidentifier, -- [OwnerSystemId] [uniqueidentifier] NOT NULL,
@p7 nvarchar(100), -- [FieldDefinitionId] [nvarchar](100) NOT NULL,
@p8 nvarchar(10), -- [Culture] [nvarchar](10) NOT NULL,
@p9 int, -- [Index] [int] NOT NULL,
@p10 nvarchar(4000), -- [BooleanValue] [bit] NULL,
@p11 nvarchar(4000), -- [DateTimeValue] [datetimeoffset](7) NULL,
@p12 nvarchar(4000), -- [DecimalValue] [decimal](18, 2) NULL,
@p13 nvarchar(4000), -- [GuidValue] [uniqueidentifier] NULL,
@p14 nvarchar(250), -- [IndexedTextValue] [nvarchar](250) NULL,
@p15 int, -- [IntValue] [int] NULL,
@p16 nvarchar(4000), -- [JsonValue] [nvarchar](max) NULL,
@p17 bigint, -- [LongValue] [bigint] NULL
@p18 nvarchar(4000) -- [TextValue] [nvarchar](max) NULL,

Further technical details

EF Core version: 1.1.0
Database Provider: Microsoft.EntityFrameworkCore.SqlServer
Operating system: Windows 10
IDE: Visual Studio 2015

[ajcvickers]

Note for triage: this happens when the value of a parameter is null. We create a default type mapping which ultimately ends up looking like nvarchar(4000). The correct mapping for the type is used for any non-null value.

[ajcvickers]

Verified that for 2.0, we don't set Size for these parameter types, and that when we do set DbType it is set to the correct value.