Problems with constrained_layout and suptitle with subfigures

Question

I am trying to create a figure in pyplot with specific gridspec, but I got into a dead end. When using subfigures it is needed to use constrained_layout = True option in the figure definition, but it disables the hspace = 0 option in the GridSpec definition.

An example looks like this:

import matplotlib.pyplot as plt
from matplotlib.gridspec import GridSpec

fig = plt.figure(
    figsize = (16,9),
    constrained_layout = True
    )

fig.suptitle("fig suptitle")


subfigs = fig.subfigures(1,3)

for sf in subfigs:
    
    sf.suptitle("subfig suptitle")
    gs = GridSpec(6,1,sf,
                  hspace = 0
                  )
    ax1 = sf.add_subplot(gs[0:2,0])
    ax1.scatter([1,1,5,2,7,5], [1,5,8,2,6,8])
    ax1.set_title("ax title")
    
    for i in range(3,6):
        ax = sf.add_subplot(gs[i,0],
                             sharex = ax1
                             )
        if i == 3:
            ax.set_title("ax title")
        ax.plot([6,2,5,5,6,8,7])
        # ax.set_title("ax title")

When I comment the constrained_layout = True line the plots are in the right possitions, but fig suptitle disappears.

Is there any workaround that keeps the fig suptitle shown and leaves hspace = 0?