Hello Julian,
I redid the steps I did during the install, and checking for the UUIDs
which show up it indeed shows one extra UUID which seems like it might have
been that other UUID.
it is a UUID of a EFI partition on the encrypted SSD which I didn't
manually tell to use in the installation.
I ran the installer again and skipped with default settings until the point
where I selected "something else" for instal location/option, and I checked
what it did.
that same partition from that UUID showed up in there, but since I didn't
manually select it I didn't expect it to be used.

however I noticed it was used by default/enabled by default by the
installer when in that manual partitioning selection, this however does
mean that it somehow didn't use the EFI partition I told it to use and just
used the first appearing EFI partition over the partition on the drive
itself.
I can see why it might be useful to automatically select such a partition
even if manual partitioning is selected, but in a case like here where 2
drives have their own EFI partition it might sometimes be confusing or
dangerous if it is automatically selected.
that said it seems like this would be something that would only ocur in
very rare cases, and so likely won't be something most users would
encounter. meaning that it would be  doubtfull weather to see it as a bug
or as a feauture. since it only used one of them and not the one I checked
to make sure it was set to be used, it might be a possible solution to
display some kind of message or error if it finds and automatically
selects(for use) 2 or more EFI partitions, that way one can be certain it
uses the right one.
since for me It showed as using that EFI partition I wanted it to use in
the installer, so I didn't check for possible other partitions in use, and
since the fstab only showed one partition I asumed there to have been no
other selected, however it had automatically selected both of them and only
used 1.

again it would be rare for something like this to happen, in my case it was
purely because I used a external SSD to avoid touching the SSD with os and
data for work and school, that way I could use that SSD to still boot into
and run ubuntu on that computer without any performance issues(since even
when used external that SSD is more than fast enough), that way I could
just use it for productivity and gaming when at home using ubuntu from that
external drive, and I could still use that other os and data on school and
work. so again a really rare thing to happen, but it might happen for
people installing it on a ssd or such using it as a portable installation
so they can use it anywhere(live usb can do so to, but has some obvious
problems, mostly speed, but sometimes also with persistency if not set up
right and with storage size typically).
but if it is easily doable a warning text or such when more than one
partition of a type from which the installer and os will only use one is
selected, will work fine as a solution, I don't think disabling the
autoselecting of EFI partitions will be great since that will affect a much
larger group, so a warning text would seem like the most easy and effective
fix right now.

so the UUID came from a internal SSD in the laptop, I asumed it didn't use
that one since I didn't manually tell it to use it, and it only used one
EFI partition in the installation, and I had the EFI partition it was
supposed to use selected to be used, then again that other one turned out
to also automatically have been selected for use.