Absolutely
The only sign that Jesus Christ would give that he was the messiah was that he would be in the "heart of the earth" the same amount of time that Jonah was in the fish:
Mat 12:38 Then some of the scribes and Pharisees said to Him, "Teacher, we want to see a sign from You."
Mat 12:39 But He answered and said to them, "An evil and adulterous generation craves for a sign; and yet no sign will be given to it but the sign of Jonah the prophet;
Mat 12:40 for just as JONAH WAS THREE DAYS AND THREE NIGHTS IN THE BELLY OF THE SEA MONSTER, so will the Son of Man be three days and three nights in the heart of the earth.
So how long was Jonah in the fish?
Jon 1:17 And the LORD appointed a great fish to swallow Jonah, and Jonah was in the stomach of the fish three days and three nights.
Your position is that Jonah was NOT literally in the fish for three days and three nights and that this is an idiom. He was really literally in the fish for only 1 day and 2 nights, you say.
So the scribes, Pharisees and an "increasing crowd" (Luke 11:29) were told by Jesus Christ that the sign that Jesus was the messiah was that he would be in the heart of the earth for 3 days and 3 nights.
This is the ONLY sign Christ gave that he was the messiah, so I'm pretty sure that you would agree that it be accurate.
So how long did the scribes and the pharisees and the increasing crowd think Jonah was really in the fish?
If it is an idiom then they had NO IDEA! The only sign that Jesus gave was a sham sign, a trick, because nobody really knew how long Jonah was in the fish. After all, there was nothing in their scripture or tradition to indicate that it was anything but a literal 3 days and 3 nights. If it wasn't, then the sign that Jesus gave that he was the messiah was a sham.
However, if they understood it to be a literal three days and three nights, then Jesus Christ HAD to be in the heart of the earth a literal three days and three nights or else he WAS NOT the messiah.
To top it off, the sign that Jesus gave was a KNOWN period of time. Being God incarnate, he knew exactly how long he would be in the heart of the earth and how long Jonah was in the fish. Yet you insist that he specified an inexact amount of time for both, preferring to use a vague idiom instead.
Your position makes no scriptural sense whatsoever. The only thing that harmonizes scripture and fulfills the sign of Jesus being the Christ was exactly what Jesus the Christ said:
Mat 12:39 But He answered and said to them, "An evil and adulterous generation craves for a sign; and yet no sign will be given to it but the sign of Jonah the prophet;
Mat 12:40 for just as JONAH WAS THREE DAYS AND THREE NIGHTS IN THE BELLY OF THE SEA MONSTER, so will the Son of Man be three days and three nights in the heart of the earth.
A literal three days and a literal three nights.