incorrect TIFF format output

[black.abbath]

MtoA-4.2.1.1 no matter what format set in "Format", there will be 32 bit tiff as result.

checked Keyshot tiff output - everything is correct.

[Stephen.Blair]

I do not reproduce that.
Check the first line of the oiiotool output, and the oiio:BitsPerSampel line:

C:\Program Files\Autodesk\Arnold\maya2019>bin\oiiotool -v --info C:\Users\blairs\Documents\maya\projects\default\images\tmp\test_operator_attr_token_int8.tif
Reading C:\Users\blairs\Documents\maya\projects\default\images\tmp\test_operator_attr_token_int8.tif
C:\Users\blairs\Documents\maya\projects\default\images\tmp\test_operator_attr_token_int8.tif :  960 x  540, 4 channel, uint8 tiff
    channel list: R, G, B, A
    compression: "lzw"
    DateTime: "2021:03:31 11:52:43"
    Orientation: 1 (normal)
    planarconfig: "contig"
    worldtocamera: -0.823136, 0.435874, 0.363952, 0, 1.49012e-08, 0.640936, -0.767594, 0, 0.567844, 0.631835, 0.527578, 0, 0, -2.98023e-07, 5.09576, 1
    worldtoscreen: -1.60054, 1.50672, 0.363955, 0.363952, 2.89745e-08, 2.21558, -0.767602, -0.767594, 1.10414, 2.18412, 0.527583, 0.527578, 0, -1.0302e-06, 4.99581, 5.09576
    oiio:BitsPerSample: 8
    tiff:Compression: 5
    tiff:PhotometricInterpretation: 2
    tiff:PlanarConfiguration: 1
    tiff:RowsPerStrip: 32

C:\Program Files\Autodesk\Arnold\maya2019>bin\oiiotool -v --info C:\Users\blairs\Documents\maya\projects\default\images\tmp\test_operator_attr_token_int16.tif
Reading C:\Users\blairs\Documents\maya\projects\default\images\tmp\test_operator_attr_token_int16.tif
C:\Users\blairs\Documents\maya\projects\default\images\tmp\test_operator_attr_token_int16.tif :  960 x  540, 4 channel, uint16 tiff
    channel list: R, G, B, A
    compression: "lzw"
    DateTime: "2021:03:31 11:52:59"
    Orientation: 1 (normal)
    planarconfig: "contig"
    worldtocamera: -0.823136, 0.435874, 0.363952, 0, 1.49012e-08, 0.640936, -0.767594, 0, 0.567844, 0.631835, 0.527578, 0, 0, -2.98023e-07, 5.09576, 1
    worldtoscreen: -1.60054, 1.50672, 0.363955, 0.363952, 2.89745e-08, 2.21558, -0.767602, -0.767594, 1.10414, 2.18412, 0.527583, 0.527578, 0, -1.0302e-06, 4.99581, 5.09576
    oiio:BitsPerSample: 16
    tiff:Compression: 5
    tiff:PhotometricInterpretation: 2
    tiff:PlanarConfiguration: 1
    tiff:RowsPerStrip: 32

C:\Program Files\Autodesk\Arnold\maya2019>bin\oiiotool -v --info C:\Users\blairs\Documents\maya\projects\default\images\tmp\test_operator_attr_token_float32.tif
Reading C:\Users\blairs\Documents\maya\projects\default\images\tmp\test_operator_attr_token_float32.tif
C:\Users\blairs\Documents\maya\projects\default\images\tmp\test_operator_attr_token_float32.tif :  960 x  540, 4 channel, float tiff
    channel list: R, G, B, A
    compression: "lzw"
    DateTime: "2021:03:31 11:57:48"
    Orientation: 1 (normal)
    planarconfig: "contig"
    worldtocamera: -0.823136, 0.435874, 0.363952, 0, 1.49012e-08, 0.640936, -0.767594, 0, 0.567844, 0.631835, 0.527578, 0, 0, -2.98023e-07, 5.09576, 1
    worldtoscreen: -1.60054, 1.50672, 0.363955, 0.363952, 2.89745e-08, 2.21558, -0.767602, -0.767594, 1.10414, 2.18412, 0.527583, 0.527578, 0, -1.0302e-06, 4.99581, 5.09576
    oiio:BitsPerSample: 32
    tiff:Compression: 5
    tiff:PhotometricInterpretation: 2
    tiff:PlanarConfiguration: 1
    tiff:RowsPerStrip: 32

[black.abbath]

checked. result (that's all output shown):

may be you have different version of Maya or Arnold?
also you can see wrong compression: zip instead of lzw