I think missing removeVerySmallKeypoints is the reason of these failure.
I will investigate what octave & 128 means. It seems to be "octave is negative", and the negative octave appears in retrieving doubled image.
I'm not sure whether these keypoints are rejected in Lowe's paper.

after adding removeVerySmallKeypoints:

$ ./bin/opencv_test_features2d --gtest_filter=SIFT/DetectorScaleInvariance.*
CTEST_FULL_OUTPUT
OpenCV version: 4.3.0-dev
OpenCV VCS version: 4.3.0-312-g2115ba82a2
Build type: Release
Compiler: /usr/bin/c++  (ver 8.3.0)
Parallel framework: pthreads (nthreads=2)
CPU features: SSE SSE2 SSE3 *SSE4.1 *SSE4.2 *FP16 *AVX *AVX2 *AVX512-SKX?
Intel(R) IPP version: ippIP AVX2 (l9) 2020.0.0 Gold (-) Oct 19 2019
OpenCL is disabled
TEST: Skip tests with tags: 'mem_6gb', 'verylong'
Note: Google Test filter = SIFT/DetectorScaleInvariance.*
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from SIFT/DetectorScaleInvariance
[ RUN      ] SIFT/DetectorScaleInvariance.scale/0, where GetParam() = ("detectors_descriptors_evaluation/images_datasets/bikes/img1.png", 0.69, 0.98)
scale = 1.5, keyPointMatchesRatio = 0.764919, scaleInliersRatio = 1
scale = 2, keyPointMatchesRatio = 0.875, scaleInliersRatio = 1
scale = 2.5, keyPointMatchesRatio = 0.757463, scaleInliersRatio = 1
[       OK ] SIFT/DetectorScaleInvariance.scale/0 (456 ms)
[----------] 1 test from SIFT/DetectorScaleInvariance (456 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (456 ms total)
[  PASSED  ] 1 test.

In fact, a lot of keypoints are rejected by this function.

scale	detected -> after removal
scale = 1 (`keypoints0`)	3384 -> 978
scale = 1.5	1748 -> 553
scale = 2	943 -> 360
scale = 2.5	733 -> 268

However, it seems that there is another reason for the failure of DescriptorScaleInvariance.
Thanks to the removal the result gets better, but it still fails.

scale	descInliersRatio w/o removal	descInliersRatio with removal
1.5	0.924645	0.974438
2	0.643913 (fail)	0.848671
2.5	0.329787 (fail)	0.595092 (fail)

Fix disabled SIFT scale invariance tests on bike image #3

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