Bug#951406: gnuplot: "-" and two 'using' doesn't work in plot/splot

[Veek]

Package: gnuplot
Version: 5.2.6+dfsg1-1+deb10u1
Severity: normal

Dear Maintainer,

   * What led up to the situation?
cat data 
17993 7555 2114 22230 11946 9761 119 5938 
24263 5803 23116 26022 2100 13260 10751 16774 
12935 31166 11077 28420 30729 5930 28746 14660 

   * What exactly did you do (or not do) that was effective (or
     ineffective)?
works, with TWO points since there are two 'using': 
gnuplot -p -e 'splot "data" u 1:2:3, "" u 1:3:4';

fails only ONE point: 
cat data|gnuplot -p -e 'splot "-" u 1:2:3, "" u 1:3:4';

   * What outcome did you expect instead?
it should display both points - one for each 'using'


-- System Information:
Debian Release: 10.3
  APT prefers stable
  APT policy: (500, 'stable'), (500, 'oldstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.19.0-8-amd64 (SMP w/4 CPU cores)
Kernel taint flags: TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=en_IN.utf8, LC_CTYPE=en_IN.utf8 (charmap=UTF-8), LANGUAGE=en_IN:en (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages gnuplot depends on:
ii  gnuplot-qt [gnuplot-x11]  5.2.6+dfsg1-1+deb10u1

gnuplot recommends no packages.

Versions of packages gnuplot suggests:
pn  gnuplot-doc  <none>

-- no debconf information