spec: fix paragraph regarding SUPI
The SUPI often is not larger than the IMSI, but the SUCI is.
diff --git a/docs/imsi-pseudo-spec.adoc b/docs/imsi-pseudo-spec.adoc
index f8e4a2b..c8d39d2 100644
--- a/docs/imsi-pseudo-spec.adoc
+++ b/docs/imsi-pseudo-spec.adoc
@@ -32,10 +32,12 @@
which uses public-key cryptography to ensure that the permanent subscriber
identity (IMSI) is not transmitted over the air interface anymore.
Rather, a concealed version of it is transmitted (3GPP TS 33.501,
-Section 6.12.2). The 5G SUCI mechanism can not be used 1:1 for previous
-generations of cellular networks as it relies on extending the
-subscriber identity from the small, 15-decimal-digit IMSI to a much
-larger SUPI (Subscriber Permanent Identifier) only available in 5G.
+Section 6.12.2). The 5G SUCI mechanism can not be adapted easily for previous
+generations of cellular networks as it relies on introducing an entirely
+new mobile identity type of larger size (SUCI) than any of the existing
+ones (e.g. IMSI), causing significant implications on protocol stacks
+and implementations all across the protocol stack of all network elements,
+including the ME.
No mechanism for increasing subscriber identity and location privacy on
the radio interface has been specified for the previous cellular