Something is terribly wrong with the sigmoid function

[NSQY]

resample_auto vs resample_manual:
https://slow.pics/c/rW8Qhc00

iew sigmoid vs fmtc sigmoid:
https://slow.pics/c/dP6VTNan

from vstools import vs, core, depth, Transfer
from vsscale.scale import SSIM
from vsscale.gamma import gamma2linear

img = core.imwri.Read('foo.png')
img = depth(img, 32)

rwidth, rheight = (178, 240)

resample_auto = SSIM(
    curve=Transfer.BT709, sigmoid=True
    ).scale(img, width=rwidth, height=rheight)

linear = img.fmtc.transfer(
    transs='709', transd='sigmoid', sig_t=0.5, sig_c=6.5)
resample = SSIM().scale(
    linear, width=rwidth, height=rheight)
resample_manual = resample.fmtc.transfer(
    transs='sigmoid', transd='709', sig_t=0.5, sig_c=6.5)


iew = gamma2linear(
    img, curve=Transfer.BT709, sigmoid=True, thr=0.5, cont=6.5
    )

fmtc = core.fmtc.transfer(
    img, transs='709', transd='sigmoid', sig_t=0.5, sig_c=6.5
    )