Nested VT-x triple fault

[mhanor]

I've tried booting nested VirtualBox VM Windows 10 1903 x64 ISO and a Windows XP 32 bit, inside a VM with two CPUs, but all I got is triple fault guru meditation, when the nested VM started.
The log is the attempt to boot the Windows 10 1903 x64 setup ISO. The nested VirtualBox was also 6.1.0beta1

[Technologov]

Level 0 = host. (Win10, 64-bit + Intel Core i7 6600U, Skylake CPU) - VBox 6.1.0-BETA1
Level 1 = 1st level of virtualization.
Level 2 = 2nd level of virtualization, going deeper into the rabbit hole.

Level 1 = Windows XP + VBox 4.1.6 (older, with official WinXP host support and VT-x enabled)
Level 2 = empty VM (VT-x enabled) -- I expected to see VirtualBox BIOS booting and that's it.

Actual results:
Crash with Guru meditation. (which means that Nested VT-x is incomplete, at least in 32-bit mode --- theoretically this should work.)