BIGFILE datafile increase causes waits on 'enq: TT - contention'

Oracle 19c on Linux (19.17)

We have a BIGFILE tablespace, size was 2.1 TB. It was increased to 2.6 TB in one operation, it took 50 min. Approx 2 min after we initiated the increase we observed one session waiting on enq: TT - contention event. 20 min later the number of waiting sessions started increasing, in 3 min there were 90 sessions waiting. Once datafile expansion completed the waits disappeared. All sessions waiting on enq: TT - contention were blocked by the session that was increasing the datafile.

As per MOS 2089689.1 this is expected behaviour: "If a tablespace has only one datafile, extent allocation will always wait while a tablespace is being resized. This is because extent allocations as well as datafile extend operations serialize on the header block of the datafile. If the tablespace has more than one datafile, then Oracle may be able to allocate the extent in another datafile without having to wait. Since a bigfile tablespace has only one datafile, extent allocations will wait if the tablespace is being resized.